Estimate of the Association of IGF-I and IGFALS Genes with Growth Traits in Hamdani Sheep

IGF-I and IGFALS play a vital stimulator role in skeletal growth, cell differentiation, metabolism, and other physiological processes. A total of 65 (male and female) animals were used in the study. Animals were measured for growth traits at birth weight, weaning weight, and weights at 6 months. The average daily gain (ADG) was calculated from birth to weaning (ADG1) and from birth to 6th month (ADG2). PCR-RFLP analysis was used to detect IGF-I polymorphism at the 5' regulatory region and IGFALS at Exon 1. Three genotypes (AA, AB and BB) were observed for IGF-I/BfoI locus with allele and genotype frequency 0.79(A) and 0.21(B); 0.71(AA), 0.15(AB) and 0.14(BB). Also, three genotypes (AA, AB and BB) were found for IGFALS/HinfI site with allele and genotype frequency as 0.22(A) and 0.78(B); 0.11(AA), 0.23(AB) and 0.66(BB). The genes were in agreement with Hardy-Weinberg equilibrium (p>0.05). Association analysis suggested that IGF-I and IGFALS significantly affected the growth traits (P<0.05). In terms of birth weight, The AA genotypes of IGF-I were higher than AB and BB. The AB genotype in terms of IGF-I had higher ADG2 compared with other genotypes. The AA genotype of the IGFALS gene was higher in terms of birth weight than other genotypes. In addition, the BB genotype was higher ADG1 than AA and BB. It is suggested that polymorphism of the IGF-I and IGFALS genes may be a potential molecular marker for growth traits in Hamdani sheep.

Keywords:
IGF-I; IGFALS; Hamdani sheep; growth traits; candidate gene

Gene	Position	Primer Sequence	FL	RE	PCR conditions	Reference
IGF-I	5' regulatory region	5'-TGAGGGGAGCCAATTACAAAGC-3' 5'-CCGGGCATGAAGACACACACAT-3'	294bp	BfoI	94°C 6m, 94°C 30s, 55°C 30s, 72°C 30s, 30 cycles 72°C 10m	He and coauthors (2012) [²³23 He J, Zhang B, Chu M, Wang P, Feng T, Cao G, et al. Polymorphism of insulin-like growth factor 1 gene and its association with litter size in Small Tail Han sheep. Mol. Biol. Rep. 2012;39(10):9801-7.].
IGFALS	Exon 1	5'-GTGAAAGCAAACAGAGCAG-3' 5'- CATTGACCACTGGAGACTG -3'	1113 bp	HinfI	95°C 5m, 95°C 45s, 57°C 45s, 72°C 45s, 35 cycles 72°C 10m	Alizadeh and coauthors (2020) [¹⁹19 Alizadeh F, Moradian F, Farhadi A. Association of allelic polymorphisms of IGFALS gene with growth traits in Makouei and Ghezel sheep breeds. Trop. Anim. Health. Prod. 2020;52(6):3027-34.].

Gene	N	Genotype Frequencies	Allele Frequencies	χ²
IGF-I	46 10 9	0.71(AA) 0.15(AB) 0.14(BB)	0.79(A) 0.21(B)	19.29
IGFALS	7 15 43	0.11(AA) 0.23(AB) 0.66(BB)	0.22(A) 0.78(B)	7.26

Traits	Genotypes (mean ± standard error)			p-value
	IGF-I
	AA	AB	BB
Birth	4.582±0.111^a	4.111±0.100^b	4.274±0.102^ab	0.009^*
Weaning 90 days	23.71±0.192^a	22.98±0.174^b	23.59±0.177^a	0.014^*
6.month weight	35.98±0.193^ab	36.22±0.175^a	35.52±0.178^b	0.025^*
ADG1	212.4±2.404	209.6±2.176	214.7±2.223	0.289
ADG2	174.4±1.159^b	178.4±1.049^a	173.7±1.071^b	0.007^*
	IGFALS
	AA	AB	BB
Birth	4.522±0.102^a	4.153±0.094^b	4.291±0.115^ab	0.034^*
Weaning 90 days	23.16±0.177	23.43±0.163	23.69±0.199	0.145
6.month weight	35.97±0.178	35.88±0.164	35.87±0.200	0.913
ADG1	207.0±2.214^b	214.2±2.047^ab	215.4±2.492^a	0.021^*
ADG2	174.7±1.067	176.3±0.987	175.5±1.202	0.574

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[1] *Correspondence: mbayraktar@cu.edu.tr; Tel.: 00905532894570 (M.B.).