Identification of MITF Gene Mutation in Porcupines: A Novel Link to Congenital Deafness and Pigmentation Disorders

Worldwide, congenital deafness and pigmentation disorders impact millions with their diverse manifestations, and among these genetic conditions, mutations in the Microphthalmia-associated transcription factor ( MITF : OMIM#156845) gene are notable for their profound effects on melanocyte development and auditory functions. We first discovered congenital deafness in mutant porcupine individuals with abnormal pigmentation among artificially bred porcupines. Their phenotypic characteristics closely resemble those of human Waardenburg Syndrome Type 2 (WS2: OMIM#193510). This study aims to establish a mutant porcupine model family for identifying candidate pathogenic genes and mutation sites, offering insights into the molecular mechanisms of human hereditary deafness. By analyzing coat color, skin, and eyes, we distinguished between different porcupine phenotypes and utilized the auditory brainstem response (ABR) method to examine and identify hearing function. Then, we used Bulk Segregant Analysis (BSA) to identify and locate the target trait genes of porcupines with pigmentary aberrations. We collected auricle skin tissue from wild type porcupines for reference-free transcriptome sequencing, and then annotated and extracted the transcript sequences of candidate genes. Finally, primers based on the identified candidate genes were designed for PCR amplification, followed by verification through Sanger sequencing. Through BSA analysis, we identified a total of 88 SNP and 336 InDel candidate sites. By annotating the MITF gene, we obtained four unique transcript sequences. The SNP and InDel sites within the porcupine MITF gene sequence, identified through BSA screening, were analyzed in conjunction with the gene's annotation results. This analysis revealed a specific mutation site, MITF c.875_877delGAA p. (Arg217del), which was subsequently verified by Sanger sequencing. This study successfully identified a mutant in porcupine that reflects the genetic and phenotypic complexity of human congenital deafness and pigmentation disorders, specifically WS2.