Polimorfizam gena hormona rasta (GH) i njegova povezanost sa svojstvima rasta u ovaca pasmine Kilakarsal

The goal of this study was to investigate the single nucleotide polymorphism of the growth hormone gene and its association with growth traits in the Kilakarsal breed of sheep. Polymerase Chain Reaction – Restriction Fragment Length Polymorphism (PCR-RFLP) of the growth hormone gene (422 bp) with HaeIII restriction enzyme revealed an A781G transition mutation at the exon 2 and the existence of two genotypes, viz., AA (366 bp and 56 bp) and AB (422 bp, 366 bp and 56 bp). The occurrence of the B allele is due to the A781G transition in the exon 2 of the growth hormone gene, which causes an amino acid change from Serine to Glycine. The genotype BB was absent in the Kilakarsal sheep population. The absence of the BB genotype at the A781G locus of the growth hormone gene in the Kilakarsal sheep population indicates that the natural selection process might be acting against this particular genotype through reduced viability or early embryonic death. Further, the statistical analysis revealed the significantly higher yearling weight of the AB than the AA genotype (P=0.038), and an appreciable difference of 1.40 kg in 9-month weight. The highly significant (P<0.001) Chi-square value (29.94) showed that the population is not the under Hardy-Weinberg equilibrium. This indicates that molecular markers associated with body weight should be explored for their use in marker assisted selection in Kilakarsal population.Cilj ovog rada bio je istražiti polimorfizam pojedinačnog nukleotida gena hormona rasta i njegovu povezanost sa svojstvima rasta u ovaca pasmine Kilakarsal. Lančana reakcija polimerazom – polimorfizam duljine restrikcijskih fragmenata (PCR-RFLP) gena hormona rasta (422 bp) s restrikcijskim enzimom HaeIII otkrila je A781G mutaciju na eksonu 2 i postojanje dvaju genotipova: AA (366 bp i 56 bp) i AB (422 bp, 366 bp i 56 bp). Navedena mutacija, osim što uzrokuje pojavu alela B, uzrokuje i promjenu aminokiseline serin u aminokiselinu glicin. Genotip BB u istražene pasmine ovaca nije pronađen. Odsutnost genotipa BB na lokusu A781G gena hormona rasta u ovaca pasmine Kilakarsal upućuje na to da prirodni process selekcije može djelovati protiv tog određenog genotipa putem smanjene sposobnosti preživljavanja ili rane embrionalne smrti. Nadalje, statistička je analiza otkrila znakovito veću tjelesnu masu genotipa AB od genotipa AA (P=0,038) i znatnu razliku od 1,40 kg u 9-mjesečnoj tjelesnoj masi istraženih ovaca. Visoko znakovita vrijednost (P<0,001) hi-kvadratnog testa (29,94) pokazala je da ova populacija ovaca ne odstupa od Hardy-Weinbergova zakona ravnoteže. To nas upućuje na zaključak da treba istražiti molekularne biljege povezane s tjelesnom masom ovaca pasmine Kilakarsal radi njihove primjene u selekciji potpomognutoj biljezima

Povezanost između novih SNP-a u egzonu 10 gena receptora hormona rasta i pokazatelja rasta u indijskih pasmina ovaca

The growth hormone receptor (GHR) gene encodes the type I cytokine receptor that helps in joining the growth hormone to this receptor, thus promoting receptor-dimerization, leading to up-regulating growth. The ovine GHR gene located on chromosome 16, which consists of 10 exons and 9 introns, along with untranslated regions on either side, comprise a total size of 178.09 kb. However, earlier reports about polymorphism have mainly dealt with exon 10 which is also a larger fragment of this gene comprising 1102 bp. Hence, this study was carried out to detect polymorphism in exon 10 of the GHR gene and its association with growth traits. Genomic DNA was isolated from blood samples of Madras Red and Mecheri sheep breeds from India. Part of exon 10 (895 bp) of the GHR gene was amplified and sent for sequencing. The sequence analysis revealed transition of nucleotide G>A at loci G177624A and G177878A in both sheep breeds. Populations were screened by Tetra-primer ARMS-PCR. The genotype frequencies of GG, GA and AA were 0.276, 0.519 and 0.205 at 177624 G>A, and 0.307, 0.444 and 0.149 at 177878 G>A in Madras Red sheep; whereas in Mecheri they were 0.476, 0.372 and 0.152 at 177624 G>A, and 0.629, 0.314 and 0.057 at 177878 G>A, respectively. Likewise the estimated allele frequencies of G and A were 0.5355 and 0.4645 at 177624 G>A, and 0.5790 and 0.4210 at 177878 G>A in Madras Red sheep; whereas in Mecheri they were 0.6620 and 0.3380 at 177624 G>A, and 0.7860 and 0.2140 at 177878 G>A, respectively. The effect of sex was significant for birth, six and nine month weight; but non-significant for three and 12 month weight in Mecheri sheep. However, in the Madras Red breed the effect of sex was significant for all body weights except weaning weight. The effect of variations on growth traits, viz., birth weight, weight at weaning, and weight at six, nine and twelve months in both breeds were analysed for their association, and they were found non-significant. Since these SNPs are salient findings of GHR gene polymorphism in Indian sheep breeds, further investigation is required into the significant effects of these novel SNPs, which could be useful for genetic improvement based on marker assisted selection.Gen receptora hormona rasta (GHR) kodira tip I citokinskog receptora koji pomaže u vezanju hormona rasta na ovaj receptor, promovirajući dimerizaciju receptora i time regulirajući rast. Ovčji gen GHR, lociran na kromosomu 16, sadržava 10 egzona i 9 introna s netranslatirajućim regijama s obje strane, tvoreći ukupnu veličinu od 178,09 kb. Dosadašnja istraživanja pokazala su da se polimorfizam nalazi većinom u egzonu 10, koji je ujedno veći fragment ovoga gena i sadržava 1102 bp. Ovo je istraživanje provedeno kako bi se otkrio polimorfizam u egzonu 10 gena GHR i njegova povezanost s pokazateljima rasta. Genomska DNA izolirana je iz uzoraka krvi ovaca pasmina Madras Red i Mecheri iz Indije. Dio egzona 10 (895 bp) gena GHR je umnožen i poslan na sekvenciranje koje je u obje pasmine ovaca pokazalo tranziciju nukleotida G > A na lokusima G177624A i G177878A. Probir populacija učinjen je pomoću Tetra-primer ARMS-PCR-a. Učestalost genotipa GG bila je 0,276, genotipa GA 0,519, a genotipa AA 0,205 na 177624 G>A, te 0,307, 0,444 i 0,149 na 177878 G>A u pasmine Madras Red. U pasmine Mecheri učestalost genotipa GG bila je 0,476, učestalost genotipa GA 0,372, a genotipa AA 0,152 na 177624 G > A, te 0,629, 0,314 i 0,057 na 177878 G > A. Učestalost alela G i A, koja je bila 0,5355 i 0,4645 na 177624 G > A, te 0,5790 i 0,4210 na 177878 G>A u ovaca Madras Red, dok je u pasmine Mecheri bila 0,6620 i 0,3380 na 177624 G>A, te 0,7860 i 0,2140 na 177878 G>A. Spol je znakovito utjecao na tjelesnu masu pri janjenju te u dobi od 6 i 9 mjeseci, no nije bilo znakovitog utjecaja u dobi od 3 i 12 mjeseci u pasmine Mecheri. S druge strane, u pasmine Madras Red spol je znakovito utjecao na tjelesnu masu u svim fazama rasta osim pri odbiću. Analizirana je povezanost varijacija s tjelesnom masom pri janjenju, odbiću te u dobi od 6, 9 i 12 mjeseci u obje pasmine, koja nije bila znakovita. Budući da su otkrića ovih SNP-a važna u proučavanju gena GHR u indijskih pasmina ovaca, potrebna su daljnja istraživanja njihova učinka koja bi mogla biti korisna u genetskom poboljšanju populaciju primjenom markerima potpomognute selekcije