Association between GNRHR, LHR and IGF1 polymorphisms and timing of puberty in male Angus cattle

Abstract

Background: In bovines, there are significant differences within and among beef breeds in the time when bulls reach puberty. Although the timing of puberty is likely to be a multigenic trait, previous studies indicate that there may also be single genes that exert major effects on the timing of puberty within the general population. Despite its economic importance, there are not many SNPs or genetic markers associated with the age of puberty in male cattle. In the present work, we selected three candidate genes, <i>GNRHR</i>, <i>LHR</i> and <i>IGF1</i>, and associated their polymorphisms with the age of puberty in Angus male cattle. Results: After weaning, 276 Angus males were measured every month for weight (W), scrotal circumference (SC), sperm concentration (C) and percentage of motility (M). A total of 4 SNPs, two within <i>GNRHR</i>, one in <i>LHR</i> and one in <i>IGF1</i> were genotyped using the pyrosequencing technique. <i>IGF1-SnaBI SNP</i> was significant associated (P < 0.01) with age at SC 28 cm, but it were not associated with age at M 10% and C 50 million. Genotype CC exhibited an average age at SC 28 cm of 7 and 11 days higher than CT (p = 0.037) and TT (p = 0.012), respectively. This SNP explained 1.5% of the genetic variance of age of puberty at SC28. <i>LHR-I499L, GNRHR-SNP5</i> and <i>GNRHR-SNP6</i> were not associated with any of the measurements. However, <i>GNRHR</i> haplotypes showed a suggestive association with age at SC 28 cm. Conclusions: The findings presented here could support the hypothesis that IGF1 is a regulator of the arrival to puberty in male calves and is involved in the events that precede and initiate puberty in bull calves. Given that most studies in cattle, as well as in other mammals, were done in female, the present results are the first evidence of markers associated with age at puberty in male cattle.