Abnormal coagulation factor VIII transcript in a Tennessee Walking Horse colt with hemophilia A.

The research article investigates the genetic cause of Hemophilia A, a blood clotting disorder, among Tennessee Walking Horse colts. Despite no apparent abnormalities found in their DNA, a potential mutation in the noncoding region of the responsible gene, Factor VIII, was suspected and traced back to the colt’s mother.

Background

• Hemophilia A is a genetic disorder in which the body’s ability to clot blood is impaired due to a deficiency in an important protein called Factor VIII (FVIII).
• This condition is predominantly observed in males as it is an X-chromosome-linked disorder, implying that the faulty gene causing this condition is present on the X chromosome.
• While the causative role of FVIII deficiency in Hemophilia A is known, the specific gene mutations responsible for the condition have not been identified.

Methods

• The study performed a detailed analysis of the genomic DNA and cDNA encoding FVIII of a Tennesee Walking Horse colt affected with hemophilia A.
• In parallel, the genomic DNA of the colt’s mother (dam) and a normal, unrelated horse were similarly analyzed.
• Using polymerase chain reactions (PCRs)—a popular biochemical technology to amplify and copy DNA—the researchers studied the hepatic cDNA from both the affected colt and an unrelated healthy horse.

Findings

• No abnormalities were observed in the splice site or coding sequence within the genomes of any of the horses involved in the study.
• Furthermore, the analysis of the cDNA revealed that the sequence between and including exon 1 and exon 2 was missing in the affected colt, whereas it was present in the healthy horse.
• This apparent deviation led the team to contemplate the existence of mutations in the noncoding region of the FVIII gene (specifically, intron 1).
• Genomic sequencing of intron 1 in both the dam and the affected colt supported the hypothesis of the mutation, suggesting that the colt could have inherited the disorder from its mother.