Cloning and characterization of the bovine somatotropin and somatostatin genes to detect selection markers

Date of Completion

January 1999

Keywords

Biology, Genetics

Degree

Ph.D.

Abstract

The objective of this study was to identify alleles of the somatotropin (ST) and somatostatin (SRIF) genes in a group of 100 dairy sires with restriction fragment length polymorphism (RFLP) analysis, and to evaluate the relationship of these alleles to measures of the genetic merit, Milk Fat Protein Dollars (MFPD) and Predictive Transmitting Ability for Milk (PTAM). Three polymerase chain reaction (PCR) cloned fragments of the ST gene were digested with MspI, PvuII, AluI, CfoI and HinfI in separate reactions. The resulting fragments were separated with electrophoresis. No mutations were detected in the promoter (from nt 2 to nt 849) region with any of the enzymes. MspI digestion of the second fragment (from nt 398 to nt 1597) detected three genotypes. The 15% heterozygous [MspI(+ –)], 1% homozygous mutated [Msp(+ +)], 83% wild type [MspI(− −)] distribution frequency agrees with most previous reports. There were no differences (p > .05) between MFPD or PTA M of the groups. Group 3 was excluded from analysis because only one individual had this genotype. Even though the MspI site in intron 3 is located near a transcription factor binding site and the [MspI (+ −)], is associated with a .9 kb insertion/deletion in the 3′ flanking region, potentially carrying transcription regulator sites, neither this, nor the [AluI(+ −)] or the presence of both [MspI(+ −)/AluI(+ −)] in the current study resulted in differences in indicators of the genetic merit. ^ The objective of the second part was to determine whether bSRIF alleles with different growth hormone release inhibiting potentials existed, bearing in mind that RFLPs in human somatostatin (hSRIF) gene have been reported. The gene (Genbank U97077), including the promoter region, exons 1 and 2, the intron and 3′ flanking region, was isolated using sequential PCR. Results of the GenBank Blast analysis revealed that the bSRIF promoter is 91% homologous to the hSRIF promoter and 90% identical to the rat and mouse SRIF promoters. Compared with hSRIF coding region, there is 95% homology among the 348 nt that code for 116 amino-acid pre-prosomatostatin. The bSRIF intron has a consensus CRE, as well as a reverse Ganuna Activated Sequence (GAS), suggesting intron-based influence of gene transcription. The lack of detection of mutations in the SRIF gene may indicate involvement in the control of transcription of most of gene sequences. Based on the results of this investigation, neither the ST nor the SRIF genes contain markers for selection of dairy sires. (Abstract shortened by UMI.)^

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