Variable number of tandem repeats in the growth hormone gene of Sparus aurata: association with growth and effect on gene transcription

The GH gene of Sparus aurata(saGH) contains variable number of tandem repeats (VNTR). The hyper‐variable minisatellites in the first and third introns segregate in a Mendelian manner and exhibit numerous alleles. Analysis by PCR and sequencing of the two introns in several wild Sparidae species revealed comparable minisatellites with some variations. ‘Zoo blot’ with the first intron unit as a probe showed this sequence to be characteristic of several families from the Perciformes order. Unexpectedly, a similar minisatellite was found in the first intron of the GH gene in flounder, which belongs to a different order. Transfection of constructs containing a reporter gene and first intron of different length to four cell lines resulted in an inhibitory effect of the longer intron relative to the short intron. A (CA)n microsatellite (saGHpCA) is found in the GH promoter. A similar repeat at the same location is present in GH promoters of several other fish species. High variability (11 alleles) of the saGHpCA was found in a hatchery population. Full‐sib family genotyping showed a Mendelian inheritance of these alleles. A significant association was found between allele distribution and body mass in large and average size fishes from a hatchery population. The intron minisatellites may serve as markers for hybrid population and parental assignment. Its presence in families and orders of the higher teleosts may help solving classification uncertainties. Their conservation and inhibitory effect suggest a biological role. The saGHpCA is correlated with growth and may be a good candidate for predicting growth performance.