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Following a classic epithelial-mesenchymal interaction developmental program, the mouse neonatal submandibular salivary gland (SMG) is comprised of large and small ducts which terminate in lumen-containing, presumptive acini that express embryonic mucin (Ball, 1974; Cutler and Gremski, 1991; Denny et al., 1997; Gresik et al., 1998; Kashimata et al., 2000a, Redman, 1987; Wessells, 1977; Jaskoll et al., 1998; Melnick and Jaskoll, 2000). Embryonic mouse SMG branching morphogenesis is best conceptualized in stages: PreBud, Initial Bud, Pseudoglandular, Canalicular, And Terminal Bud (Jaskoll and Melnick, 1999; Fig. 1). In the PreBud Stage, SMG development begins as a thickening of the primitive oral cavity epithelium adjacent to the developing tongue. During the Initial Bud Stage, this thickened epithelium grows down into the first branchial (mandibular) arch mesenchyme to form the initial SMG bud. With continued epithelial proliferation and downgrowth, the SMG primordium becomes a solid, elongated epithelial stalk terminating in a bulb; this SMG primordium is surrounded by condensed mesenchyme. The primordium branches by repeated furcation at the distal ends of successive buds to produce a bush-like structure comprised of a network of elongated epithelial branches and terminal epithelial buds surrounded by loosely packed mesenchyme (the Pseudoglandular Stage). These branches and buds hollow out by epithelial cell apoptosis during the Canalicular and Terminal Bud Stages to form the ductal system and presumptive acini (for details, see Jaskoll and Melnick, 1999; Melnick and Jaskoll, 2000). Epithelial cell proliferation is found in all stages, even after well-defined lumen formation in the Terminal Bud Stage. Epithelial cell apoptosis begins with the onset of lumen formation in the Canalicular Stage. Moreover, our studies suggest that ductal canalization is primarily due to caspase 8-mediated apoptosis whereas p53 primarily mediates terminal bud lumina formation (Melnick and Jaskoll, 2000; Melnick et al., 2001 a, b; Table 1). In addition, although we found three pro-survival/anti-apoptotic proteins (NF-κB, bcl2, and survivin) in lumen-bounding epithelial cells during luminization, the presence of only nuclear-localized (activated) survivin in the layer of surviving cells is seen after the completion of lumen formation (Jaskoll et al., 2001). Based on our data, we conclude that apoptosis-mediated lumen formation and cell survival are achieved through several different pathways.

Embryonic SMG cell proliferation, cell quiescence, apoptosis, and histodifferentiation events are mediated by specific growth factors, cytokines, and transcription factors which are expressed at specific times and locations (Hardman and Spooner, 1994; Kashimata and Gresik, 1997; Kashimata et al., 2000a, b, Jaskoll and Melnick, 1999; Melnick et al., 2001a, b; Jaskoll et al., 2002). Although it has conclusively been shown that SMG morphogenesis is dependent on epithelial-mesenchymal interactions (see reviews, Wessells, 1977; Cutler and Gremski, 1991), little was known about which molecules are involved in the induction and regulation of early embryonic SMG branching. To begin to delineate the key molecules and signaling pathways involved in the induction and regulation of embryonic SMG morphogenesis, we have determined the stage-specific distribution of multiple growth factors and cytokines (and their receptors) and transcription factors, and correlated their expression pattern with cell proliferation and apoptosis (Fig. 1; Jaskoll and Melnick, 1999; Melnick and Jaskoll, 2000; Jaskoll et al., 2002; Table 1). Functional studies in our laboratory and others support this conclusion (Hardman and Spooner, 1994; Kashimata and Gresik, 1997; Kashimata et al., 2000a, b, Jaskoll and Melnick, 1999, Melnick and Jaskoll, 2000; Melnick et al., 2001a, b, c; Jaskoll et al., 2002, De Moerlooze et al., 2000; Ohuchi et al., 2000).

Figure 2. Connections Map. This signaling map reflects the pathways investigated in our laboratory. Known and putative connections are based on work in ours and other laboratories.

The cellular and extracellular components of these key signaling pathways may be visualized as a Connections Map (Fig. 2) which details the functional relationships within and between pathways. The promotional and inhibitory, synergistic and antagonistic, molecular interactions noted are supported by an enormous experimental effort by numerous laboratories worldwide.

The SMG phenotype in a wide variety of transgenic and mutant mice has been analyzed (Table 2). Importantly, disruption of Fgfr2-IIIb and Fgfr2-IIIc expression indicates that FGF-R2-IIIb and FGF-R2-IIIc signaling play key roles during embryonic SMG development. The presence and subsequent death of Fgfr2-IIIb^-/- Initial Bud Stage SMG epithelial cells (Table 2; DeMoerlooze et al., 2000) indicates that FGFR2-IIIb signal transduction is essential for Pseudoglandular Stage development but not initial bud formation. By contrast, our demonstration of hypoplastic SMGs in Fgfr2-IIIc mice indicates that FGFR2-IIIc plays an essential role during branching morphogenesis. Moreover, since sonic hedge hog (SHH) has been shown to be a downstream target of FGFR2-IIIb-mediated signaling (Revest et al., 2001) and FGF and SHH exhibit a feedback mechanism (Laufer et al., 1994), we evaluated the SMG phenotype in Shh^-/- mice in collaboration with Peter Carlsson (Goteborg University, Sweden). Shh null SMGs are severely dysplastic. Importantly, the observation of no SMGs in Fgfr2-IIIb null mice and dysplastic SMGs in Shh null mice is consistent with the fact that FGFR2-IIIb signals through multiple downstream pathways in addition to SHH. Further, since the forkhead gene Foxf1 is a downstream target of SHH signaling (Mahlapuu et al., 2001) and Foxf1^+/- mutant mice exhibit lung and foregut abnormalities, we have also investigated the SMG phenotype in Foxf1 mutant mice in collaboration with Peter Carlsson. [Note that the Foxf1 null mutation is embryolethal; thus we evaluated Foxf1^+/- SMGs]. Foxf1^+/- SMGs are hypoplastic Given the above, we conclude that both SHH/Foxf1 signaling play key roles during embryonic SMG development. Moreover, our demonstration of dysplastic and hypoplastic SMGs in Shh^-/- and Foxf1^+/- mice, respectively, is consistent with fact that SHH signals through multiple downstream target genes, not only Foxf1 (Mahlapuu et al., 2001; see review, Ingham and McMahon 2001).

Regarding other signaling pathways, our observations of an abnormal SMG phenotype in Pax6 and Bmp7 null mice (Table 2) indicates that Pax6 and Bmp7are essential for embryonic SMG branching morphogenesis, but not initiation. In addition, given that one of the functions of TACE is the proteolytic activation of TGF-α, the sole EGF-R ligand in pre-Canalicular SMGs, our analyses of Tace and Egfr null mice provide solid evidence that the EGF-R pathway is not essential for SMG initiation, but is essential for normal post Canalicular Stage branching morphogenesis (Table 2). By contrast, the presence of normal SMGs in Tgfβ2, Tgfβ3, Msx2 and Hox-a5 null mice indicates that TGF-β2, TGF-β3, Msx-2, and Hox-a5 are not essential for SMG morphogenesis (Table 2). Finally, since N-myc null mutations are embryo lethal (Stanton et al., 1992), we evaluated N-myc's role in transgenic mice (N-myc^9a/9a) which underexpress the N-myc gene, exhibit marked lung abnormalities, and die at birth (Moens et al., 1992). The similarity of SMGs in N-myc^9a/9a transgenic and wild-type mice indicates that N-myc is not a sine qua non of embryonic SMG development.

Finally, given that: (1) mutations in ectodysplasin (EDA) or its mouse homologue Eda give rise to the syndrome hypohidrotic ectodermal dysplasia (HED), characterized by absence or hypoplasia of teeth, hair, and sweat glands, and (2) a similar phenotype is seen in downless (Edar^dl) mutant mice due to mutations in the ectodysplasin receptor (Edar) gene (Gruneberg, 1965, 1971; Kere et al., 1996; Srivastava et al., 1997; Monreal et al., 1998), we postulated that Eda/Edar signal transduction may also play a key role during SMG development. We evaluated the Eda-less Tabby (Eda^Ta) and the Edar-less downless (Edar^dl) mutant mouse strains and found abnormal SMG phenotypes in both mutant strains (Table 2). Eda^Ta (Tabby) SMGs are hypoplastic, with a marked decrease in intercalated ducts and acini, as well as a notable decline in acinar-specific mucin expression. By contrast, Edar^dl (downless) SMGs are dysplastic, characterized by an absence of ducts, acini, and mucin protein. Significantly, our observation that Eda^Ta (Tabby) and Edar^dl (downless) SMGs are abnormal indicates that Eda/Edar-mediated signal transduction is essential to SMG development. Moreover, the presence of SMGs in both Ta and dl mutant mice indicate that Eda/Edar signaling is important for branching morphogenesis and histodifferentiation, but not initial gland formation.

Functional Analysis of TNF, IL-6, NF-κB, and TGF-β-RII Mediated Signaling

In our laboratory, we have investigated the morphoregulatory role during embryonic SMG development for each of the following signaling pathways:

(1) TNF/TNF-R1 Signal Transduction. We utilized in vitro experiments to investigate the phenotypic outcomes of enhanced and deficient TNF ligand (Melnick et al., 2001a). TNF supplementation induced a significant 3-fold increase in cell proliferation and a highly significant 2-fold increase in epithelial branching compared to controls. In addition, a 2/3 reduction in endogenous TNF protein levels resulted in a highly significant 2/3 decline in SMG epithelial cell proliferation and a significant 6-fold increase in apoptosis. Our data indicates that the TNF/TNF-R1 signal transduction pathway plays an important role in balancing cell proliferation and apoptosis during SMG duct and presumptive acini formation.

(2) IL-6 Signal Transduction: We investigated the phenotypic outcomes of enhanced and decreased IL-6 signaling in vitro (Melnick et al., 2001b) and found: (1) IL-6 supplementation induces a substantial increase in overall size and in number of ductal branches and terminal buds, as well as a highly significant increase in epithelial cell proliferation and (2) SMG explants cultured with anti-IL-6 neutralizing antibodies exhibited a marked decrease in epithelial ducts and terminal buds, concomitant with a highly significant 60% decline in cell proliferation and a highly significant 13-fold increase in apoptosis. Our data indicates that IL-6 signaling is important to SMG developmental homeostasis.

(3) NF-κB-Mediated Transcription and Protein Expression: Since the TNF-R1/NF-κB cascade is the primary pathway induced by TNF ligand/receptor binding, we then investigated the role of NF-κB during embryonic SMG morphogenesis (Melnick et al., 2001c). We interrupted NF-κB activation using the cell permeable peptide SN50. SN50-inhibition of NF-κB nuclear translocation in E15 SMG primordia cultured for 2 (E15+2) days results in an highly significant 10-fold increase in apoptosis and 81% decline in cell proliferation. The increase in apoptosis is associated with a highly significant > 4-fold increase in activated p53.

Using transcriptome and proteome analyses, we identified those transcripts and proteins in our cognate Connections Map that have altered expression with NF-κB inhibition. cDNA expression array analysis of 1176 genes revealed significant changes in expression for 691 genes (-60%). Among these, genes encoding other transcription factors and those genes associated with signal transduction, cell cycle progression, cell adhesion, and apoptosis exhibited 1.5 or greater-fold change in mRNA levels (Melnick et al., 2001c).

Unable to extrapolate from RNA abundance to relevant protein levels, since this would ignore changes in translational efficiency or protein stability, we analyzed NF-κB-inhibited and control SMG explants using 2-D Western Multiprotein Arrays. This technique allows for the analysis of - 600 signal transduction and other proteins simultaneously in each independent sample. Proteomic analyses demonstrated notable qualitative and quantitative differences in protein expression between control and NF-κB E15+2 explants (Melnick et al., 2001c). We detect 18 proteins with a 1.5 or greater-fold change in expression with NF-κB inhibition and specifically related to the Connections Map. Importantly, they include signal transduction, translation control (checkpoint), cell cycle, and apoptosis proteins that are downstream from activation of the TNF, IL-6, EGF, IGF, and FGF signaling pathways. PNN analyses of transcriptomic and proteomic assays identified specific transcripts and proteins with altered expression that best discriminate control from SN50-treated SMGs. These include PCNA, GR, BMP1, BMP3b, Chk1, Caspase 6, E2F1, ERK1/2, and JNK, as well as several others of lesser importance ( Melnick et al., 2001c).

Finally, we focused our attention on two particularly important pathways relative to cell proliferation and apoptosis, ERK 1/2 and Caspase 3. Downstream of activated ERK 1/2 is an upregulation of cell proliferation proteins and potentially enhanced cell division; downstream of activated Caspase 3 are the sequellae of apoptosis, including PARP cleavage and inhibition of DNA repair, DNA fragmentation, and nuclear membrane fragmentation. To determine if these key pathways were activated in the absence of NF-κB nuclear translocation, we quantitated the level of activated (phosphorylated/cleaved ) ERK 1, ERK 2, c-Raf, Caspase 3, and PARP (Melnick et al., 2001c); all proteins except c-Raf are significantly (p<0.05) increased in SN50-treated explants. Paradoxically, increased ERK 1/2 activation is associated with virtually no change in the antecedent activation of Raf. Although we find an increase in total Raf protein, no increase in activated c-Raf is found, indicating that increased total protein level is not always indicative of increased protein activation.  

Taken together, our results indicate that NF-κB-mediated transcription is critical to embryonic developmental homeostasis. Inhibition of NF-κB nuclear translocation alters the expression of a genetic network of broadly related, rather than independent, components. Our results also demonstrate how informative it can be regarding organogenesis to simultaneously evaluate the gene and protein expression of multiple genes from multiple pathways within broad functional categories.

(4) TGF-β-RII mediated signal transduction: Although our studies of null mice indicate that neither TGF-β2 nor TGF-β3 expression is essential for embryonic SMG development (Jaskoll et al., 1999),  we could not exclude the possibility that one TGF-β isoform compensates for another in these null mice. To address this question, we cultured embryonic SMG primordia in the presence of antisense oligodeoxynucleotides (ODNs) designed against TGF-β-RII, the cognate receptor for all TGF-β isoforms (Fig. 3). Anti-TGF-β-RII ODNs induced an - 40% increase in branching compared to sense or nonsense ODNs (compare Fig. 3B to 3A.).To confirm that TGF-β-RII signaling was interrupted in this set of experiments, we cultured embryonic SMG primordia in the presence of TGF-β2 supplementation or TGF-β2 + antisense ODN supplementation (Fig. 2C, D). TGF-β2 supplementation induced an -50% reduction in branch number (Fig.3C). By contrast, TGF-β2 supplementation failed to inhibit branching morphogenesis in the presence of TGF-β-RII antisense ODNs (Fig. 3D). This result indicates that anti-TGF-β-RII ODNs interrupted TGFβ/TGF-β-RII signal transduction.

Figure 3. Antisence interruption of TGF-β/ TGF-β-RII signal transduction results in a marked increase in branching. A marked increase in branching is seen between antisense (B) and nonsense (A) ODN-treated E13 + 3 explants. TGF-β2 supplementation (0.5 ng/ml, R & D) of E13+3 SMG (C) decreases SMG branching. However, no decrease in branching is seen in the presence of TGF-β2 + AS ODN (D), indicating that TGF-β/TGF-β-RII signaling is interrupted.

Cloning, Sequencing and Functional Analysis of Embryonic SMG Mucin

Prior to investigating which factors regulate mucin expression during embryonic SMG development, we determined embryonic SMG mucin mRNA and protein expression (Jaskoll et al., 1998, Melnick et al., 2000d). Mucin transcripts are localized throughout branching epithelia in Pseudoglandular Stage and older SMGs, with increased hybridization signal being seen in terminal bud and proacinar epithelial cells. By contrast, SMG mucin protein is not immunodetected until Terminal Bud Stage, being primarily immunolocalized to terminal bud and proacinar epithelial cell membranes. Our observation of mucin transcripts throughout early embryonic SMG epithelia compared to mucin protein’s restricted distribution in terminal bud and proacinar epithelia suggests that mucin transcription and/or translation is likely downregulated in nonterminal bud (ductal) epithelia.

Importantly, Northern and Western blot analyses demonstrated notable differences between embryonic and adult SMG mucin mRNA and protein (Jaskoll et al., 1998). E17 SMGs exhibited two unique mucin transcripts (0.85 and 1.20 kb) which are approximately 19% greater or smaller in size than the single (1.01 kb) adult transcript; substantial protein differences were also seen. To characterize embryonic SMG mucin, we cloned and sequenced the embryonic mouse low molecular weight mucin (GenBank accession # AF247816; Melnick et al., 2001d). The cDNA encodes a 885 bp sequence and a 220 aa protein (~ 25 kDa), rich in potential O-glycosylation sites, and variably glycosylated. Significantly, embryonic low molecular weight mucin is an alternately spliced variant of adult Muc10. Consensus secondary structure prediction for embryonic low molecular weight mucin is consistent with a molecule that is anchored to the plasma membrane, directly or indirectly, and has a protein core that serves as a scaffold for carbohydrate presentation. Given that saliva is nonfunctional in utero and is only utilized after birth with the onset of feeding, we also determined the timing of the transition from the embryonic to adult form. Both embryonic and adult mucin protein variants are immunodetected in newborn and 21 day SMGs, with a marked increase in adult forms being seen between the newborn and 21-day old gland. The predominance of adult mucin proteins is correlated with the appearance of acinar cell histodifferentiation which occurs 2-3 weeks after birth (Srinivasan and Chang, 1979).

The specificity and expression pattern of embryonic mucin suggested that it may play a morphogenetic role. Since lectins and other glycoproteins play important roles in cell adhesion during organogenesis (Mann and Waterman, 1998), and selectins bind mucins or mucin-like proteins (Lasky et al., 1992; Prakobphol et al., 1998, 1999), we postulated that one possible function of the embryonic low molecular weight mucin is to bind L-selectin. Immunoprecipitation and Western blot analyses demonstrate that embryonic, but not adult, mucin is able to bind L-selectin and does so endogenously (Melnick et al., 2001d). Since the primary role of L-selectin is to mediate weak cell adhesion prior to strong adhesion mediated by integrins (Kaltner and Stierstoffer, 1998; Shimizu and Shaw, 1993) and its ligands are mucin-like glycoproteins, we suggest that this low molecular weight embryonic mucin is a MucCam (mucin cell adhesion molecule).

Studies in our laboratory has demonstrated that exogenous glucocorticoids (CORT) treatment in utero induces a significant increase in mucin mRNA and protein expression (Melnick and Jaskoll, 2000). In addition, our in vitro experiments also indicates that CORT is required for normal embryonic mucin protein expression (Melnick and Jaskoll, 2000).Given that mucin transcripts are distributed throughout all epithelia in the Pseudoglandular and Canalicular Stages whereas mucin protein is expressed only in Terminal Bud Stage epithelia (Jaskoll et al., 1998), our results suggest that CORT downregulates mucin transcription and/or translation in ductal epithelia during SMG development. In addition, we also find that IL-6, but not TNF, signaling modulates embryonic mucin expression in vitro (Melnick et al., 2001a, b). As part of our ongoing research projects, we continue to investigate which growth factor-mediated signaling pathways modulate embryonic SMG mucin expression.

Ball WD: Development of the rat salivary glands. III. Mesenchymal specificity in the morphogenesis of the embryonic submaxillary and sublingual glands of the rat. J Exp Zool 1974, 188:277-288.

Celli G, LaRochelle WJ, Mackem S, Sharp R, Merlino G: Soluble dominant-negative receptor uncovers essential roles for fibroblast growth factors in multi-organ induction and patterning. EMBO J 1998, 17:1642-1655.

Cutler LS, Gremski W:Epithelial-mesenchymal interactions in the development of salivary glands. Crit Rev Oral Biol Med 1991, 2:1-12.

De Moerlooze L, Spencer-Dene B, Revest J-M, Hajihosseini M, Rosewell I, Dickson C: An important role for the IIIb isoform of fibroblast growth factor receptor 2 (FGFR2) in mesenchymal-epithelial signalling during mouse organogenesis. Development 2000, 127:483-492.

Denny PC, Ball WD, Redman RS: Salivary glands: a paradigm for diversity of gland development. Crit Rev Oral Biol Med 1997, 8:51-75.

Gresik EW, Kashimata M, Kadoya Y, Yamashina S: The EGF system in fetal development. Eur. J. Morphol. 1998, 36 :

Gruneberg H: Genes and genotypes affecting the teeth of the mouse. J. Embryol. Exp. Morphol. 1965, 14:137-159.

Hajihosseini MK, Wilson S, De Moerlooze L, Dickson C: A splicing switch and gain-of-function mutation in FgfR2-IIIc hemizygotes causes Apert/Pfeiffer-syndrome-like phenotypes. Proc. Natl. Acad. Sci. 2001, 98:3855-60.

Hardman P, Landels E, Woolfe A, Spooner B: TGF-β1 inhibits growth and branching morphogenesis in embryonic mouse submandibular and sublingual glands in vitro. Dev. Growth Diff. 1994, 36:567-577.

Ingham, P.W.A., McMahon, A.P. Hedgehog signaling in animal development: paradigms and principles. Genes Devel. 2001, 15:3059-3087.

Jaskoll T, Chen H, Denny P, Denny P, Melnick M: Mouse submandibular gland mucin: embryo-specific mRNA and protein species. Mech. Dev. 1998, 74:179-183.

Jaskoll T, Melnick M: Submandibular gland morphogenesis: stage-specific expression of TGF-alpha, EGF, IGF, TGF-β, TNF and IL-6 signal transduction in normal mice and the phenotypic effects of TGF-β2, TGF-β3, and EGF-R null mutations. Anat. Rec. 1999, 256:252-268.

Jaskoll T, Zhou Y-M, Chai Y, Makarenkova HP, Collinson JM, West JD, Hajihosseini MK, Lee J, Melnick M: Embryonic submandibular gland morphogenesis: stage-specific protein localization of FGFs, BMPs, Pax 6 and Pax 9 and abnormal SMG phenotypes in Fgf/R2-IIIc, BMP7 and Pax6 mice. Cells, Tissues, Organs 2002, 270:83-98.

Jaskoll T, Chen H, Zhou Y-M, Wu D, Melnick M: Developmental expression of survivin during embryonic submandibular salivary gland development. BMC Developmental Biology 2001, 1:5 <http://www.biomedcentral.com/1471-1213x/1471/1475>.

Jernvall J, Thesleff I: Iterative signaling and patterning during mammalian tooth morphogenesis. Mech. Dev. 2000, 92:19-29.

Kaltner, H. and Stierstorfer, B: Animal lectins as cell adhesion molecules. Acta Anat. 1998, 161: 162-179.

Kashimata M, Gresik E: Epidermal growth factor system is a physiological regulator of development of the mouse fetal submandibular gland and regulates expression of the α6-integrin subunit. Develop. Dyn. 1997, 208:149-161.

Kashimata M, Sayeed S, Ka A, Onetti-Muda A, Sakagami H, Faraggiana T, Gresik E: The ERK-1/2 signaling pathway is involved in the stimulation of branching morphogenesis of fetal mouse submandibular glands by EGF. Developmental Biology 2000a, 220:183-196.

Kashimata MW, Sakagami HW, Gresik EW: Intracellular signaling cascades activated by the EGF receptor and/or integrins, with potential relevance for branching morphogenesis of the fetal mouse submandibular gland. Eur. J. Morphol. 2000b, 38:269-275.

Kere J, Srivastava A, Montonen O, Zonana J, Thomas N, Ferguson B, Munoz F, Morgan D, Clarke A, P B, Ellson Y, Ezer S, Saarialho-Kere U, de la Chapelle A, Schlessinger D: X-linked anhidrotic (hypohidrotic) ectodermal dysplasia is caused by mutation in a novel transmembrane protein. Nat. Genet. 1996, 13:409-416.

Laufer, E., Nelson, C.E., Johnson, R.L., Morgan, B.A., Tabin, C: Sonic hedgehog and Fgf-4 act through a signaling cascade and feedback loop to integrate growth and patterning of the developing limb bud. Cell 1994, 79:993-1003.

Mahlapuu M, Enerback S, Carlsson P: Haploinsufficency of the forkhead gene Foxf1, a target of sonic hedgehog signaling, causes lung and foregut malformations. Development 2001, 128:2397-2406.

Mann, P.L. and Waterman, R.E: Glycocoding as an information management system in embryonic development. Acta Anat. 1998, 161, 153-161.

Melnick M, Jaskoll T: Mouse submandibular gland morphogenesis: a paradigm for embryonic signal processing. Crit. Rev. Oral Biol. 2000, 11:199-215.

Melnick M, Chen H, Zhou Y-M, Jaskoll T: Embryonic mouse submandibular salivary gland morphogenesis and the TNF/TNF-R1 signal transduction pathway. Anat. Rec. 2001a, 262:318-320.

Melnick M, Chen H, Zhou Y, Jaskoll T: Interleukin-6 signaling and embryonic mouse submandibular salivary gland morphogenesis. Cells, Tissues, Organs 2001b, 168:233-245.

Melnick M, Chen H, Zhou Y, Jaskoll T: The Functional Genomic Response of Developing Embryonic Submandibular Glands to NF-κB Inhibition. BMC Developmental Biology. 2001c, 1:15 <http://www.biomedcentral.com/1471-213X/1/15>.

Melnick M, Chen H, Zhou Y, Jaskoll T: Embryonic mouse submandibular salivary gland mucin: an alternately spliced Muc10 glycoprotein ligand for putative L-selectin mediated epithelial cell adhesion during terminal bud differentiation. Arch. Oral Biol. 2001d, 46:745-757.

Moens, C., Auerbach, A., Conlon, R., Joyner, A. and Rossant, J.: A targeted mutation reveals a role for N-myc in branching morphogenesis in the embryonic mouse lung. Genes Dev 1992, 6: 691-704.

Monreal A, Ferguson B, Headon D, Street S, Overbeek P, Zonana J: Mutations in the human homolog of the mouse dl cause autosomal recessive and dominant hypohidrotic ectodermal dysplasia. Nat. Genet. 1999, 22:366-369.

Ohuchi H, Hori Y, Yamasaki M, Harada H, Sekine K, Kato S, Itoh N: FGF10 acts as a major ligand for FGF receptor 2 IIIb in mouse multi-organ development. Bioch. Biophys. Res. Comm. 2000, 277:643-649.

Prakobphol, A., Thomsson, K.A., Hansson, G.C., Rosen, S.D., Singer, M.S., Phillips, N.J., Medzihradszky, K.F., Burlingame, A.L., Leffler, H. and Fisher, S.J: Human low-molecular-weight salivary mucin expresses sialyl Lewis^X determinant and has L-selectin ligand activity. Biochemistry 1998, 37: 4916-4927.

Prakobphol, A., Tangemann, K., Rosen, S.D., Hoover, C.I., Leffler, H. and Fisher, S.J: Separate oligosaccharide determinants mediate interactions of the low-molecular-weight salivary mucin with neutrophils and bacteria. Biochemistry 1999, 38: 6817-6825.

Redman RS: Development of the salivary glands. In: The Salivary System. Sreebny LM, ed. Boca

Raton, FL: CRC Press, 1987 pp. 1-20.

Revest J-M, Spencer-Dene B, Kerr K, De Moerlooze L, Roswell I, Dickson C: Fibroblast growth factor receptor-2-IIIb acts upstream of Shh and Fgf4 and is required for Limb bud maintenance but Not for the induction of Fgf8, Msx1, or Bmp4. Devel. Biol. 2001, 231:47-62.

Shimizu, Y., Shaw, S: Mucins in the mainstream. Nature 1993, 336: 630-631.

Stanton, B.R., Perkins, A.S., Tessarollo, L., Sassoon, D.A., Parada, L.F. (1992) Loss of N-myc function results in embryonic lethality and failure of the epithelial component of the embryo to develop. Genes Dev 1992, 6: 2235-2247.

Srinivasan R, Chang W: The postnatal development of the submandibular gland of the mouse. Cell Tissue Res. 1979, 198:363-371.

Srivastava A, Pispa J, Hartung A, Du Y, Ezer S, Jenks T, Shimada T, Pekkanen M, Mikkola M, Ko M, Thesleff I, Kere J, Schlessinger D: The Tabby phenotype is caused by mutation in a mouse homologue of the EDA gene that reveals novel mouse and human exons and encodes a protein (ectodysplasin-A) with collagenous domains. Proc. Natl. Acad. Sci. 1997, 94:13069-13074.

Wessells N: Tissue interactions and development. Menlo Park, CA: Benjamin Cummins, 1977.

Yang A, Schweitzer, Sun D, Kaghad M, Walker N, Bronson RT, Tabin C, Sharpe A, Caputs D, Crum C, McKeon F: p63 is essential for regenerative proliferation in limb, craniofacial and epithelial development. Nature 1999, 398:714-718.

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