F8a, in the context of hemophilia A, is a particular DNA sequence. One copy of the F8A gene is located within intron 22 of the factor VIII (FVIII) coagulation gene, and two other copies are 500 kb upstream. The FVIII gene is crucial as mutations in it cause hemophilia A, an X-linked genetic disease and a common coagulation disorder [1].

A common molecular inversion in the FVIII gene, involving homologous recombination between the intragenic F8A gene copy and either the distal or proximal copy, occurs in about 50% of unrelated patients with severe hemophilia A. This inversion leads to severe hemophilia A as no intact FVIII is produced and can be diagnosed by Southern blot analysis. The inversion almost exclusively originates in male germ cells [1].

In summary, F8a, through its role in the FVIII gene inversions, is significantly associated with the development of severe hemophilia A. Understanding the function of F8a in the context of the FVIII gene is vital for the molecular diagnosis and potential genetic counseling in families with hemophilia A patients.

References:

1. De Brasi, C D, Slavutsky, I R, Larripa, I B. . [Molecular genetics of hemophilia A]. In Medicina, 56, 509-17. doi:. https://pubmed.ncbi.nlm.nih.gov/9239887/