A novel mutation in Hr causes abnormal hair follicle morphogenesis in hairpoor mouse, an animal model for Marie Unna Hereditary Hypotrichosis.

Hairpoor mice (Hr(Hp)) were derived through N-ethyl-N-nitrosourea (ENU) mutagenesis. These mice display sparse and short hair in the Hr(Hp)/+ heterozygous state and complete baldness in the Hr(Hp)/Hr(Hp) homozygous state. This phenotype was irreversible and was inherited in an autosomal semidominant manner. Hair follicles (HFs) of Hr(Hp)/+ mice underwent normal cycling and appeared normal, although smaller than those of the wild-type mice. In contrast, HFs of Hr(Hp)/Hr(Hp) mice became cyst-like structures by postnatal day (P) 21. The number and length of vibrissae decreased in a dose-dependent manner as the number of mutant alleles increased. A positional candidate gene approach was used to identify the gene responsible for the hairpoor phenotype. Genetic linkage analysis determined that the hairpoor locus is 2 cm from D14Mit34 on chromosome 14. Sequence analysis of the exons of the candidate gene hairless revealed a T-to-A transversion mutation at nucleotide position 403 (exon 2), presumably resulting in abolishment of an upstream open reading frame (uORF). In addition, we also found that the near-naked mouse (Hr(N)), a spontaneously arising mutant, harbors a A402G transition in its genome. Both mutations were in the uATG codon of the second uORF in the 5' UTR and corresponded to the mutations identified in Marie Unna Hereditary Hypotrichosis (MUHH) patients. In the present study we describe the phenotype, histological morphology, and molecular etiology of an animal model of MUHH, the hairpoor mouse.

Implications for tooth development on ENU-induced ectodermal dysplasia mice.

BACKGROUND: In this study, the mutated phenotypes were produced by treatment of chemical mutagen, N-ethyl-N-nitrosourea (ENU). We analyzed the mutated mice showing the specific phenotype of ectodermal dysplasia (ED) and examined the affected gene. METHODS: Phenotypes, including size, bone formation, and craniofacial morphology of ENU-induced ED mice, were focused. Tooth development and expression of several molecules were analyzed by histologic observations and immunohistochemistry. We carried out genome-wide screening and quantitative real-time PCR to define the affected and related genes. RESULTS: As examined previously in human ectodermal dysplasia, ENU-induced ED mice showed the specific morphologic deformities in tooth, hair, and craniofacial growth. Tooth development in the ENU-induced ED mice ceased at early cap stage. In addition, skeletal staining showed retardation in craniofacial development. Finally, the affected gene, which would be involved in the mechanism of ED, was located between the marker D3Mit14 and D3Mit319 on chromosome 3. CONCLUSIONS: The affected gene in ENU-induced ED mice showed several defects in ectodermal organogenesis and these results indicate that this gene plays an important role in mouse embryogenesis.

Studies on the Small Body Size Mouse Developed by Mutagen N-Ethyl-N-nitrosourea.

Mutant mouse which show dwarfism has been developed by N-ethyl-N-nitrosourea (ENU) mutagenesis using BALB/c mice. The mutant mouse was inherited as autosomal recessive trait and named Small Body Size (SBS) mouse. The phenotype of SBS mouse was not apparent at birth, but it was possible to distinguish mutant phenotype from normal mice 1 week after birth. In this study, we examined body weight changes and bone mineral density (BMD), and we also carried out genetic linkage analysis to map the causative gene(s) of SBS mouse. Body weight changes were observed from birth to 14 weeks of age in both affected (n = 30) and normal mice (n = 24). BMD was examined in each five SBS and normal mice between 3 and 6 weeks of age, respectively. For the linkage analysis, we produced backcross progeny [(SBS × C57BL/6J) F1 × SBS] N2 mice (n = 142), and seventy-four microsatellite markers were used for primary linkage analysis. Body weight of affected mice was consistently lower than that of the normal mice, and was 43.7% less than that of normal mice at 3 weeks of age (P < 0.001). As compared with normal mice at 3 and 6 weeks of age, BMD of the SBS mice was significantly low. The results showed 15.5% and 14.1% lower in total body BMD, 15.3% and 8.7% lower in forearm BMD, and 29.7% and 20.1% lower in femur BMD, respectively. The causative gene was mapped on chromosome 10. The map order and the distance between markers were D10Mit248 - 2.1 cM - D10Mit51 - 4.2 cM - sbs - 0.7 cM - D10Mit283 - 1.4 cM - D10Mit106 - 11.2 cM - D10Mit170.

A novel missense mutation in the mouse hairless gene causes irreversible hair loss: genetic and molecular analyses of Hr m1Enu.

A novel autosomal recessive mutant was produced using N-ethyl-N-nitrosourea mutagenesis. The characteristics of the mutant mice included progressive irreversible hair loss within a month of birth, wrinkled skin, and long curved nails. Linkage analysis revealed that the causative gene is linked to D14Mit193 on chromosome 14. Sequence analysis of the complete cDNA of the candidate gene, hairless (Hr), identified a homozygous G-to-T transition at nucleotide 3572, leading to the substitution of glycine by tryptophan, designated Gly960Trp. This missense mutation occurs in the vicinity of repression domain 3 of the hairless protein (HR). This allele was named Hr(m1Enu). The relative amounts of Hr mRNA and HR protein determined by real-time PCR and Western blot analyses, respectively, were slightly elevated in the mutant mice. Quantitative real-time PCR analysis revealed the increased expression of Kc1 and Vdr in the mutant mice, whereas the expression of Nrs1 and Krtap16-6 was decreased. These results suggest that the Gly960Trp substitution in HR protein in Hr(m1Enu) mice may alter the function of HR as a transcriptional corepressor.