Document Type : Research Paper
Authors
1 Department of Animal Science, Faculty of Agriculture, University of Tehran, Karaj, Iran. E-mail: p.azizi@ut.ac.ir
2 Corresponding Author, Department of Animal Science, Faculty of Agriculture, University of Tehran, Karaj, Iran. E-mail: hmoradis@ut.ac.ir
3 Department of Animal Science, Faculty of Agriculture, University of Tehran, Karaj, Iran. E-mail: moradim@ut.ac.ir
4 Department of Animal Science, Faculty of Agriculture, University of Tehran, Karaj, Iran. E-mail: sara.nejadi@ut.ac.ir
Abstract
Objective: Leptin is a peptide hormone secreted by adipose tissue and also associated with feed intake, growth, and lipid metabolism. The aim of this study was to investigate the polymorphism of the 271 base pair locus, including the entire exon 2 and part of intron 2 of the leptin gene in two sheep breeds, Lori-Bakhtiari and Zel-Atabay crossbreds, and to determine the relationship of this locus with carcass traits and identify desirable genotypes for these traits in the studied sheep.
Methods: In the present study blood samples were collected from 114 sheep, including 74 Lori-Bakhtiari lambs from the industrial slaughterhouse in Farsan County and 40 Zel-Atabay crossbred sheep from the industrial slaughterhouse in Gorgan County. DNA extraction was performed using an optimized salt method. Polymerase chain reaction (PCR) was performed to amplify a 271 base pair fragment encompassing exon 2 and part of intron 2 of the leptin gene. Examination of this fragment using the single-strand conformation polymorphism (SSCP) method revealed nine banding patterns. Following sequencing of the observed banding patterns, comparison with the reference sequence identified six genotypes. To investigate the association between genotypes and the studied traits, genotype effect was included as an independent variable in the models.
Results: Sequencing identified three mutations in this region: the (A/G) 1416 mutation observed in Iranian breeds, another mutation in the coding region where a cytosine base is inserted (+C 1328), resulting in a truncated protein, and the third mutation in intron 2, where thymine is replaced by guanine at nucleotide 1566. Allele frequencies in Lori-Bakhtiari and Zel-Atabay crossbred sheep were 0.552 and 0.788 for the first mutation (+C 1328), 0.359 and 0.00 for the second mutation (A/G 1416), and 0.179 and 0.121 for the third mutation (T/C 1566), respectively. Comparison of the obtained sequences with NCBI database sequences identified six genotypes. Evaluations in this study showed significant relationships between the identified genotypes in Lori-Bakhtiari sheep and traits such as chest circumference, animal height, upper and middle tail circumference, upper and middle tail width, and blood triglyceride levels. In Zel-Atabay crossbreds, significant relationships were observed between the identified genotypes and traits such as carcass weight and lower tail circumference.
Conclusions: The findings demonstrate that the leptin gene polymorphisms at the 271-bp locus, particularly the +C1328 and A/G1416 mutations, can serve as effective molecular markers in sheep breeding programs to improve carcass traits (such as increased carcass weight and optimized fat distribution). These results highlight the importance of targeting this genomic region for superior animal selection in breeding and herd management.
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