Identification of citrullinaemia carrier and detection of a new silent mutation at 240bp position in ASS1 gene of normal Holstein cattle

摘要

The autosomal recessive genetic disorders are regularly investigated especially in Indian Holstein and Holstein Crossbred bulls before they entered in semen collection so that a defective gene should not be transmitted to future generations. Bovine citrullinaemia first reported in Australia is a metabolic disorder as one of the enzymes, Argininosuccinate synthetase (ASS) involved in urea cycle is impaired in function. The mutation responsible for citrullinemia has been characterized as a single-base substitution at 256bp (C>T) in coding exon 3 of argininosuccinate synthetase 1 (ASS1) gene, which converts the CGA (arginine) at 86 codon to TGA (stop codon). A Holstein bull during routine molecular screening was found to be carrier for Citrullinaemia that was confirmed by sequencing. This is a fresh case of Citrullinaemia carrier in addition to three cases reported earlier in India. Partial sequencing of coding exon 3 of a normal Holstein revealed a new silent polymorphism at 240bp position that does not change amino acid (Sarine AGC>AGT) at 80 codon within exon 3 of ASS1 gene. The sequence of exon 3 of ASS1 gene in a normal Holstein exhibiting a new polymorphism was submitted to NCBI with accession No. KF933365. The presence of citrullinaemia carriers in Indian Holstein, though in very low frequency, emphasizing to continue the investigation of mutant gene in cattle population.