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|Coordinate||20,451,862 bp (GRCm38)|
|Base Change||T ⇒ A (forward strand)|
|Gene Name||desmoglein 4|
|Chromosomal Location||20,436,175-20,471,821 bp (+)|
|MGI Phenotype||Mice carrying mutations at this locus exhibit abnormalities in hair growth, vibrissae growth, and a thickened epidermis.|
|Amino Acid Change||Valine changed to Glutamic Acid|
|Institutional Source||Beutler Lab|
|Gene Model||predicted sequence gene model|
AA Change: V211E
|Predicted Effect||possibly damaging
PolyPhen 2 Score 0.814 (Sensitivity: 0.84; Specificity: 0.93)
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Recessive|
|Local Stock||Live Mice|
|Last Updated||11/16/2016 1:15 PM by Anne Murray|
|Record Created||01/08/2016 11:36 AM by Jamie Russell|
The burrito phenotype was identified among G3 mice of the pedigree R4012, some of which showed hair loss on their abdomens and backs near their ears (Figure 1).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 79 mutations. The hair loss phenotype was linked to a mutation in Dsg4: a T to A transversion at base pair 20,451,862 (v38) on chromosome 18, or base pair 15,688 in the GenBank genomic region NC_000084 for the Dsg4 gene. Linkage was found with a recessive model of inheritance (P = 1.257 x 10-5), wherein four affected mice were homozygous for the variant allele, and 32 unaffected mice were either heterozygous (N = 19) or homozygous (N = 13) for the reference allele (Figure 2).
The mutation corresponds to residue 766 in the NM_181564 mRNA sequence in exon 6 of 16 total exons.
The mutated nucleotide is indicated in red. The mutation results in a valine (V) to glutamic acid (E) substitution at position 211 (V211E) in the DSG4 protein, and is predicted by PolyPhen-2 to be damaging (score = 0.814).
DSG4 is a member of the desmoglein family of cadherins. Dsg4 is part of the desmosomal cadherin gene cluster on chromosome 18. The mouse genome gene cluster includes: Dsc3—Dsc2—Dsc1—Dsg1β (Dsg5)—Dsg1α—Dsg1γ (Dsg6)—Dsg4—Dsg3—Dsg2 (1). Mouse and human DSG4 share 79% amino acid identity and 86% homology.
DSG4 has four N-terminal extracellular cadherin repeats, an extracellular anchoring domain (EA), a transmembrane domain, an intracellular anchoring domain (IA), an intracellular cadherin-specific sequence (ICS), a linker domain, three intracellular repeated unit domains, and a C-terminal domain (Figure 3) (2;3). DSG4 has five putative calcium-binding sites (DXNDN or A/VXDXD) and five N-linked glycosylation consensus motifs (NXS/T). The calcium coordinating pocket that mediates assembly of cadherin partners (4).There are three conserved repeats: DIIVTE, NVVVTE, and NVYYAE; the function of the repeats is unknown.
The burrito mutation results in a valine (V) to glutamic acid (E) substitution at position 211 (V211E); residue 211 is within the second cadherin repeat.
DSG4 is expressed in the suprabasal epidermis as well as throughout the matrix, precortex, and inner root sheath of the hair follicle (5). Dsg4 is expressed in the anagen stage hair follicles in mouse skin (5). In vibrissae follicles, DSG4 is expressed in the cells of the matrix, precortex, and inner root sheath (5).
HOXC13, LEF1, and FOXN1 transcription factors repress Dsg4 transcription. HOXC13, LEF1, and FOXN1 are members of the Notch pathway, indicating that the Notch pathway is involved in the activation and/or maintenance of Dsg4 expression in the hair follicle (6).
The skin serves an important function as a barrier to the environment, and maintains its integrity by continuously renewing the epidermis, while also maintaining associated structures such as hair. The surface epithelium of the skin is composed primarily of keratinocytes and is constantly regenerated as cells in the outer cornified layer are sloughed off and replaced by newly differentiated cells. Hair is produced and maintained by the pilosebaceous unit consisting of a hair-producing follicle and a sebaceous gland composed of many different cell types. The hair follicle can be divided into 3 regions: the lower segment (bulb and suprabulb), the middle segment (isthmus), and the upper segment (infundibulum). Eight epithelial layers are present in the hair follicle including the outer root sheath (ORS) that is continuous with the epidermis, the companion layer (CL), the inner root sheath (IRS) consisting of three layers (Henle’s, Huxley’s and cuticle) and the hair shaft, which also consists of three layers (cuticle, cortex and medulla). After hair follicles are established, hair is periodically shed and then replaced, involving periodic destruction and regeneration of hair follicles. The hair cycle is divided into periods of follicle growth (anagen), followed by regression (catagen) and rest (telogen). During the regression phase, the lower half of the follicle undergoes apoptosis. During the anagen phase, hair follicle growth is reinitiated as follicle stem cells are induced to proliferate. A number of signaling pathways are implicated in skin and hair follicle morphogenesis and regeneration including Sonic hedgehog (Shh), Wnts, and TGF-β family members.
Desmosomes are multiprotein complexes that link cadherin to the intermediate filament, providing structural support for tissues that undergo mechanical stress. The desmocolins (Dsc1-3) and DSGs are the adhesion molecules of desmosomes, intercellular junctions that anchor the hair shaft to the hair follicle, and are collectively known as desmosomal cadherins (Figure 4). Within desmosomes, the extracellular domains of desmocolins and desmogleins from neighboring cells form heterophilic interactions in the extracellular space, while intracellularly they are linked to plakoglobin, plakophilins, and desmoplakin. Desmoplakin binds to keratin intermediate filaments, thereby tethering the intermediate filaments to the plasma membrane to physically strengthen the junction. Dsg4 functions in an adhesive role mainly in hair follicles, while the other members of the Dsg family show variable tissue expression (e.g., Dsg2 is expressed in all tissues that have desmosomes, and Dsg1 and Dsg3 are expressed in the stratified squamous epithelia) (5).
A spontaneous mutation in Dsg4 occurs in the lanceolate hair (lah) (5;7) and lanceolate hair-J (lahJ) mouse models (8). The mutation in the lahJ mice is a single base pair insertion after nucleotide 746 within exon 7, resulting in a frameshift and insertion of three aberrant amino acids followed by a premature stop codon. The mutation in the lah mice is an A to C transversion at base pair 587. The mutation results in conversion of tyrosine 196 to a serine. The lah and lahJ mice exhibited variable hair loss, including vibrissae, but hair remained on the head and shoulders (5;8). The lahJ mice were runted, while the lah mice were not (5;7;8). With age, the skin of the mice wrinkled, and the mice developed a noninflammatory, proliferative skin disease with follicular dystrophy. The hair fibers exhibited periodic nodules along the shaft, compaction, spiral fractures, broken tips, and lance-shaped tips. In addition to the visible phenotypes, the lah and lahJ mice also exhibit elevated levels of IgE in the serum. Mutations in rat Dsg4 lead to a similar phenotype as that observed in the mouse (9-11). Hair loss in the lah rat begins at approximately 2 weeks of age, until at 4 weeks the rats are completely bald. Hair regrowth begins after an approximate 29-day cycle of growth and loss. The epiderms of the lah rat exhibits increased proliferation (9). The skin of the Dsg4 mutant rats is thickened with a concomitant increase in basal cell proliferation; the dermis is highly collagenous (10). The hair shaft and inner root sheath exhibit irregularities, and the outer root sheath is wider than normal in some hair follicles.
Humans with mutations in DSG4 exhibit autosomal recessive hypotrichosis 6 [LAH; OMIM: #607903; (12-16)], which is characterized by hypotrichosis of the scalp, chest, arms, and legs. Hair follicles and shafts in patients with LAH are aberrant. Typical hairs in the patients with LAH are fragile and break away easily, leaving short sparse scalp hairs. LAH affects the trunk and extremities as well as the scalp, eyebrows, and eyelashes.
The burrito mice exhibit hair loss similar to the lah mouse models, indicating loss of DSG4burrito function.
burrito(F):5'- CTCAAGGAAGTCGGGAAAATTC -3'
burrito(R):5'- GGTGCATAAAACGAAATCTGTATCAC -3'
burrito_seq(F):5'- CTTTTTATACCTAATGCCTGGAGG -3'
burrito_seq(R):5'- TAAAACGAAATCTGTATCACTGACC -3'
1. Whittock, N. V. (2003) Genomic Sequence Analysis of the Mouse Desmoglein Cluster Reveals Evidence for Six Distinct Genes: Characterization of Mouse DSG4, DSG5, and DSG6. J Invest Dermatol. 120, 970-980.
2. Wheeler, G. N., Parker, A. E., Thomas, C. L., Ataliotis, P., Poynter, D., Arnemann, J., Rutman, A. J., Pidsley, S. C., Watt, F. M., and Rees, D. A. (1991) Desmosomal Glycoprotein DGI, a Component of Intercellular Desmosome Junctions, is Related to the Cadherin Family of Cell Adhesion Molecules. Proc Natl Acad Sci U S A. 88, 4796-4800.
3. Koch, P. J., Walsh, M. J., Schmelz, M., Goldschmidt, M. D., Zimbelmann, R., and Franke, W. W. (1990) Identification of Desmoglein, a Constitutive Desmosomal Glycoprotein, as a Member of the Cadherin Family of Cell Adhesion Molecules. Eur J Cell Biol. 53, 1-12.
4. He, W., Cowin, P., and Stokes, D. L. (2003) Untangling Desmosomal Knots with Electron Tomography. Science. 302, 109-113.
5. Kljuic, A., Bazzi, H., Sundberg, J. P., Martinez-Mir, A., O'Shaughnessy, R., Mahoney, M. G., Levy, M., Montagutelli, X., Ahmad, W., Aita, V. M., Gordon, D., Uitto, J., Whiting, D., Ott, J., Fischer, S., Gilliam, T. C., Jahoda, C. A., Morris, R. J., Panteleyev, A. A., Nguyen, V. T., and Christiano, A. M. (2003) Desmoglein 4 in Hair Follicle Differentiation and Epidermal Adhesion: Evidence from Inherited Hypotrichosis and Acquired Pemphigus Vulgaris. Cell. 113, 249-260.
6. Bazzi, H., Demehri, S., Potter, C. S., Barber, A. G., Awgulewitsch, A., Kopan, R., and Christiano, A. M. (2009) Desmoglein 4 is Regulated by Transcription Factors Implicated in Hair Shaft Differentiation. Differentiation. 78, 292-300.
7. Montagutelli, X., Hogan, M. E., Aubin, G., Lalouette, A., Guenet, J. L., King, L. E.,Jr, and Sundberg, J. P. (1996) Lanceolate Hair (Lah): A Recessive Mouse Mutation with Alopecia and Abnormal Hair. J Invest Dermatol. 107, 20-25.
8. Sundberg, J. P., Boggess, D., Bascom, C., Limberg, B. J., Shultz, L. D., Sundberg, B. A., King, L. E.,Jr, and Montagutelli, X. (2000) Lanceolate Hair-J (lahJ): A Mouse Model for Human Hair Disorders. Exp Dermatol. 9, 206-218.
9. Jahoda, C. A., Kljuic, A., O'Shaughnessy, R., Crossley, N., Whitehouse, C. J., Robinson, M., Reynolds, A. J., Demarchez, M., Porter, R. M., Shapiro, L., and Christiano, A. M. (2004) The Lanceolate Hair Rat Phenotype Results from a Missense Mutation in a Calcium Coordinating Site of the Desmoglein 4 Gene. Genomics. 83, 747-756.
10. Meyer, B., Bazzi, H., Zidek, V., Musilova, A., Pravenec, M., Kurtz, T. W., Nurnberg, P., and Christiano, A. M. (2004) A Spontaneous Mutation in the Desmoglein 4 Gene Underlies Hypotrichosis in a New Lanceolate Hair Rat Model. Differentiation. 72, 541-547.
11. Bazzi, H., Kljuic, A., Christiano, A. M., Christiano, A. M., and Panteleyev, A. A. (2004) Intragenic Deletion in the Desmoglein 4 Gene Underlies the Skin Phenotype in the Iffa Credo "Hairless" Rat. Differentiation. 72, 450-464.
12. Schaffer, J. V., Bazzi, H., Vitebsky, A., Witkiewicz, A., Kovich, O. I., Kamino, H., Shapiro, L. S., Amin, S. P., Orlow, S. J., and Christiano, A. M. (2006) Mutations in the Desmoglein 4 Gene Underlie Localized Autosomal Recessive Hypotrichosis with Monilethrix Hairs and Congenital Scalp Erosions. J Invest Dermatol. 126, 1286-1291.
13. Shimomura, Y., Sakamoto, F., Kariya, N., Matsunaga, K., and Ito, M. (2006) Mutations in the Desmoglein 4 Gene are Associated with Monilethrix-Like Congenital Hypotrichosis. J Invest Dermatol. 126, 1281-1285.
14. Wajid, M., Bazzi, H., Rockey, J., Lubetkin, J., Zlotogorski, A., and Christiano, A. M. (2007) Localized Autosomal Recessive Hypotrichosis due to a Frameshift Mutation in the Desmoglein 4 Gene Exhibits Extensive Phenotypic Variability within a Pakistani Family. J Invest Dermatol. 127, 1779-1782.
15. Ullah, A., Raza, S. I., Ali, R. H., Naveed, A. K., Jan, A., Rizvi, S. D., Satti, R., and Ahmad, W. (2015) A Novel Deletion Mutation in the DSG4 Gene Underlies Autosomal Recessive Hypotrichosis with Variable Phenotype in Two Unrelated Consanguineous Families. Clin Exp Dermatol. 40, 78-84.
|Science Writers||Anne Murray|
|Illustrators||Diantha La Vine, Katherine Timer|
|Authors||Lauren Prince, Jamie Russell, and Bruce Beutler|
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