Assignment of the fibroblast growth factor 10 (FGF10) gene to bovine chromosome 20q16-->q17 by fluorescence in situ hybridization and somatic cell panel analysis.

Tetradysmelia is an inherited defect observed in Holstein cattle (Kühn et al., 2002) characterized by complete lack or extremely severe reduction of all limb constituents distal of scapula and pelvic girdle. Due to the marked similarity in phenotype between fibroblast growth factor (Fgf10)–/– knockout mice (Min et al., 1998) and tetradysmelia calves, FGF10 was a strong candidate gene for the bovine defect. In humans FGF10 is localized on HSA5p13→p12 in close vicinity to the growth hormone receptor (GHR) gene. Bovine GHR was genetically mapped to the middle part of BTA20 (Barendse et al., 1997). Comparative mapping (Everts-van der Wind et al., 2004) confirmed the chromosomal homology between HSA5 and the centromeric and middle part of BTA20, indicating that FGF10 should be located in the middle part of BTA20. Multipoint likelihood homozygosity mapping, however, excluded the middle part of BTA20 as locus for tetradysmelia (Kühn et al., 2002). Proof of the assumed genomic localization of FGF10 in the middle part of BTA20 unambiguously excludes FGF10 as the causal gene underlying the genetic defect tetradysmelia in cattle despite its strong candidacy.