BÚSQUEDA DE POLIMORFISMOS EN LA REGIÓN FLANQUEANTE 5´DEL GEN 1GF-1 Y SU ASOCIACIÓN CON LOS NÍVELES DE ARNm, PROTEÍNA Y GANANCIA DE PESO EN CORDEROS

FLORES ENCINAS, LUIS ÁNGEL (2019) BÚSQUEDA DE POLIMORFISMOS EN LA REGIÓN FLANQUEANTE 5´DEL GEN 1GF-1 Y SU ASOCIACIÓN CON LOS NÍVELES DE ARNm, PROTEÍNA Y GANANCIA DE PESO EN CORDEROS. Maestría thesis, Universidad Autónoma de Chihuahua.

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Resumen

The insulin-like growth factor 1 gene (IGF-1) encodes the IGF-1 protein, which in turn plays a key role in muscle development in both, the pre-natal and post-natal stages of animals. Thus, it has been described in several studies as a candidate marker gene for growth traits. The objective of this study was to investigate the presence of single nucleotide polymorphisms (SNPs) in the 5’ flanking region of IGF-1 and its association with gene expression levels, blood circulating IGF-1 hormone, daily weight gain (GDP) and total gain of weight (GTP) in lambs. The study was executed in three phases. In Phase 1, a search of SNPs was performed by PCR and sequencing of a 265 bp region upstream the transcription start site of the IGF-1 gene. Then, 22 lambs were genotyped by PCR-RFLPs for the variant herein reported and IGF-1 concentration, GDP and GTP were measure. The two alleles obtained were called A and B, generating the genotypes AA, BB and AB, for homozygous for the variant, homozygous wild type and heterozygous, respectively. In Phase 2, the gene expression of 12 Dorper females with different genotypes randomly selected were analyzed by qPCR. In Phase 3, 81 Dorper females were genotyped and GDP and GTP were measured. The statistical analysis in all phases was performed in SAS program. In Phase 1, the sequence analysis revealed changes from guanine to cytosine at position 85 and from guanine to adenine at position 87. The frequency of allele A was 0.66 while for allele B was 0.34. The genotypic frequencies were 0.50, 0.32 and 0.18 for the AA, AB and BB, respectively. GTP was lower (P < 0.05) in carrier animals (22.16 ± 1.07 kg) compared with the non-carrier ones (26.75 ± 1.2 kg). IGF-1 concentration was lower (P < 0.05) in carrier animals compared with non-carrier lambs at 14 d (168.76 ± 15.01 vs 229.95 ± 16.78 ng mL-1), 42 d (191.02 ± 38.28 vs 324.50 ± 42.80 ng mL-1) and 70 d (209.18 ± 30.63 vs 375.87 ± 34.2 ng mL-1) of feeding test. Phase 2: gene expression was 2.7-fold change lower (P < 0.05) in carrier than in the non-carrier ones. The GDP and GTP were not different (P > 0.05) in Phase 3. Animals carrying the IGF-1 gene variant herein reported had lower levels of IGF-1 gene expression and IGF-1 protein concentration in serum compared to non-carriers. However, additional experiments are needed to relate to phenotypic characteristics, such as carcass traits, diameter and muscle fibers density.

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