Orientation And Analysis Of YYHL Hairless Gene Mutation Point

In 1990, Four hairless mice were found from KM(kunming) experiment mice' reproducing group in the Lab Animal Center of Henan. 10 years later, the first inbred strain of hairless mice in China was founded, and it was named Yuyi hairless mice (for short: YYHL).these mice developed a normal first pillage up to the age of 3 weeks, at which time they began to lost their fur coat in a cephalocaudal pattern The hair loss was normally completed within 1 week except of their beard, after which the animals remain naked all their lives accompanied by thymus' s premature degeneration, skins premature aging, shortened life span (about 12 months) and abnormalities in immunology and reproduction. YYHL has the similar appearance to hairless mice reported abroad. According to the analysis of genetic spectrum ,it has been confirmed that the hairless mutation is autosomal recessive allelic mutation that maps to mouse chromosome 14.However, the function of hairless gene has remained largely unexplored. Limin found the hr gene of YYHL was the same with KM mice from nucleotide 3150 to 3565(Genbank accession number Z32675), further more the partial hr gene of YYHL shared 100% identity with that of KM mice, 95%, with Rat, 84% with human. The result proved that the hr gene mutation didn't happen in this segment and the hr gene was altitudinal conservative. We continue the research to find the hrgene mutation of YYHL. Methods:We designed three pairs of primers based on the available murine cDNA sequence of hairless gene (Genbank accession number Z32675).Then we cloned and sequenced partial hairless gene of YYHL. In order to find the mutation point we compared the partial DNA sequence and amino acid of hairless gene of YYHL to that of KM mice, Mus musculus (house mouse) respectively. Results:1. Cloning and sequencing of partial hr gene of YYHL and KM miceThe DNA fragment sequenced of YYHL mice contains 3556bp, KM mice 3549bp. They include 6 exons (exon 9,10,11, 12and partial exon 8,13)and 5 introns (introns8,9,10,ll,12).2. Comparison of partial hr gene between YYHL and KM miceThere are 58 differences between the two DNA sequences. Four gene mutations were considered to be important in our research, including two insertion (AACT in intron 8, CTCCATCG in intron 9),one deletion (AAGA in intron 8)and one nonsense mutation in exon 12 (3300G A). The last one results in the introduction of a premature termination codon UGA.The partial hr gene of YYHL shares 97.7% identity with that of KM mice,99.4% with Mus musculus.3. The amino acid sequence of YYHL hr gene compared with KM mice and Mus musculus .The hr gene sequenced in this experiment of KM mice and Mus musculus codes 246 amino acids, YYHL 225 amino acids terminated in the 225th amino acid .( Genbank accession number Z32675 the 910th amino acid) . Conclusions:1. The partial hr gene of YYHL shares 97.7% identity with that of KM mice, 99.4% with Mus musculus. Which suggests the hr gene isaltitudinal conservative.2. Four important changes probably influence the hr protein and hr character, including three insertion/deletion and one nonsense mutation in exon 12. The detailed mechanism will probably be illuminated in the future.3. In addition, there are many other changes between the hr gene of YYHL and KM mice in this result. If they are significative must be invalidated in the future. Until the whole hr gene are cloned we will know If there are change at other sites of YYHL hr gene.