Background and Aim: Jacob sheep are a rare ancient breed of sheep believed to have originated from the Mediterranean area but which are now kept throughout the world. These sheep have recently attracted medical interest due to the observation of a genetic disorder in the breed that can be used as an animal model of Tay–Sachs disease (TSD). This study aims to detect mutations in the Hexosaminidase A gene in Jacob sheep based on sequence analysis of the 284-bp fragment situated between exon 11 and intron 11 of the gene, a target sequence for site-specific mutation. This is the first study that has investigated Jacob sheep in Bulgaria for gene-specific mutations.

Materials and Methods: A total of 20 blood samples were collected from Jacob sheep from the Rhodope Mountains. DNA was isolated from these samples, and a specific 284-bp fragment was amplified. The amplified products were purified using a polymerase chain reaction purification kit and sequenced in both directions.

Results: Target sequences were successfully amplified from all 20 investigated sheep. Sequence analysis did not show the homozygous, recessive, missense (G-to-C transition) mutation at nucleotide position 1330 (G1330→C) in exon 11, demonstrating that all of these sheep were a normal genotype (wild-type).

Conclusion: Jacob sheep are considered a potentially useful animal model in advancing the understanding of pathogenesis and developing potential therapies for orphan diseases, such as those characterized by mutant GM2 gangliosides. The clinical and biochemical features of the Jacob sheep model of TSD represent well the human classical late-infantile form of this disorder, indicating that the model can serve as a possible new research tool for further study of the pathogenesis and treatment of TSD.

Keywords: GM2 gangliosides, Hexosaminidase A gene, human replacement therapy, Jacob sheep, Tay–Sachs disease.