F5 and hyperinsulinemic hypoglycemia, familial, 4: Interestingly, factor-V-deficiency is caused by mutations in the F5 gene, located on the long (q) arm of chromosome 1 at position 23, nearby LEFTY2 (Left-Right Determination Factor 2), playing a role in left-right asymmetry determination of organ systems during development at cytogenetic location 1q42.1 [35].