Genetic Disease Testing

Genetic Disease Testing

In animal breeding, genetic disorders are one of the most important issues for breeders. These are monogenic recessive autosomal defects which causes early embryonic mortality, abortion or death at early age after birth. Widespread use of artificial insemination (AI) and international trading of semen and breeding bulls accelerates the spread of undesirable genes in population. Regular screening of the breeding bulls used for Artificial Insemination reduces the risk of dissemination of these deleterious genes in the animal population. Four major genetic disorders namely Bovine Leukocyte Adhesion Deficiency (BLAD), Citrullinaemia, Deficiency of Uridine Monophosphate Synthase (DUMPS) and Factor XI deficiency syndrome are tested in the laboratory.

I.  Bovine Leukocyte Adhesion Deficiency (BLAD)

BLAD is a disease characterized by a reduced expression of the adhesion molecules on neutrophils, called β-integrins. These proteins help the neutrophils to migrate to the site of inflammation. Animals with BLAD are characterized by recurrent bacterial infections, pneumonia, ulcerative and granulomatous stomatitis, enteritis with bacterial overgrowth, periodontitis, loss of teeth, delayed wound healing, persistent neutrophilia and death at an early age.

BLAD RFLP

Method of Testing: DNA Extraction from blood – Amplification of the gene (PCR) – Restriction Enzyme digestion of PCR product (RFLP) – Gel Electrophoresis – Interpretation.

II.  Citrullinaemia

Bovine Citrullinaemia is an autosomal recessive inherited disorder of urea cycle that is lethal in early postnatal period. It is a consequence of a deficiency of argininosuccinate synthase (ASS), one of the enzymes of the urea cycle. Calves affected with bovine citrullinaemia appear normal immediately after birth. However, between the 3rd and 5th day, the disease progresses rapidly. Death usually occurs within 12 hours of onset of these clinical signs. The clinical signs of citrullinaemia are believed to be a consequence of accumulation of ammonia in the brain of the affected calves.

Citrullinaemia RFLP

Method of Testing: DNA Extraction from blood – Amplification of the gene (PCR) – Restriction Enzyme digestion of PCR product (RFLP) – Gel Electrophoresis – Interpretation.

III. Deficiency of Uridine Monophosphate Synthase (DUMPS)

DUMPS is a hereditary lethal autosomal disorder causing early embryonic mortality during implantation in the uterus. In mammalian cells, the last step of pyrimidine nucleotide synthesis involves the conversion of orotate to uridine monophosphate synthase (UMPS) and is catalysed by UMP synthase enzyme. The mutation in a gene for UMPS leads to a premature stop codon, which subsequently produces a functionally impaired enzyme. The embryos appear to be aborted or reabsorbed approximately 40 days after conception, leading to repeat breeding problems.

DUMP RFLP

Method of Testing: DNA Extraction from blood – Amplification of the gene (PCR) – Restriction Enzyme digestion of PCR product (RFLP) – Gel Electrophoresis – Interpretation.

IV.  Factor XI Deficiency syndrome

Factor XI (FXI) is one of more than a dozen proteins involved in the early blood coagulation cascade. FXI deficiency syndrome is caused by an insertion of 76bp segment within exon 12 of the FXI gene. Heterozygous individuals with FXI deficiency have serious health problems. On the other hand both heterozygous and homozygous animals for this mutation have susceptibility to some diseases such as mastitis, metritis and pneumonia and also have lower calving and survival rates.

Factor XI PCR

Method of Testing: DNA Extraction from blood – Amplification of the gene (PCR) –Gel Electrophoresis – Interpretation.