In other species: dog , horse

Possibly relevant human trait(s) and/or gene(s) (MIM number): 306900

Mendelian trait/disorder: yes

Mode of inheritance: X-linked

Considered a defect: yes

Key variant known: yes

Year key variant first reported: 2005

Cross-species summary: Also called factor IX deficiency or Christmas disease. This is one of the two X-linked bleeding disorders, haemophilia A being the other. The fact that these two disorders are X-linked in all species reported to date provides strong support for Ohno's suggestion that the X chromosome has been highly conserved throughout evolution.

Molecular basis: By sequencing an obvious candidate gene (F9), Goree et al. (2005) reported different causative mutations in two affected cats: "Affected cat 1 had a single nucleotide change in exon 8 at the 1st nucleotide position of the codon encoding an arginine (CGA to TGA) at amino acid position 338. This mutation would be predicted to result in the appearance of a premature stop codon in the portion of the gene encoding much of the catalytic domain of the protein. Affected cat 2 had a single nucleotide change in exon 4 at the 2nd nucleotide position of the codon encoding amino acid 82 (TGT to TAT), which would be predicted to result in the substitution of a tyrosine for a cysteine. This substitution would likely result in disruption of a disulfide bond crucial to normal protein structure and function"

Associated gene: