Genotyping and Nucleotide Sequences of Growth Hormone Releasing Hormone and its Receptor Genes in Egyptian Buffalo

Aim: The hypothalamic hormone, growth hormone-releasing hormone, is the principal stimulator of pituitary growth hormone (GH) synthesis and secretion. GHRH and its receptor (GHRHR) provide important functions in the regulation of the GH axis and in the development and proliferation of pituitary somatotropic axis. This study aimed to identify the genotypes and nucleotide sequences of two multifunctional genes; growth hormone-releasing hormone (GHRH) and its receptor (GHRHR) in Egyptian buffalo.

Methodology: Genomic DNA was extracted from blood samples of 100 healthy buffaloes maintained at the Mahlet Mussa and El-Gmeasa herds from 2010 to 2012. PCR was performed using primers flanking a 296-bp fragment from GHRH gene and a 425-bp fragment from GHRHR gene of Egyptian buffalo. The PCR-amplified fragments were digested with HaeIII (GHRH) and Eco57I (GHRHR), electrophoresed and analyzed on agarose gels stained with ethidium bromide. The two amplified fragments were also sequenced and aligned with published sequences.

Results: Depending on the presence of the restriction site at 241^242 position (GG^CC) in 296-bp amplified fragments of GHRH, we genotyped all tested buffalo animals as AA. Due to the absence of the restriction site at position 300^301 ([CTGAAG(N)16^] in the amplified fragment of GHRHR (425-bp), we genotyped the tested animals as AA. The Egyptian buffalo GHRH and GHRHR nucleotide sequences were submitted to NCBI/Bankit/GenBank and have the accession numbers JN967799 and KC295414, respectively.

Conclusion: The Egyptian buffaloes are characterized by best production traits like high milk fat content as well as higher average daily gain and body weight where they are possess with fixed GHRHAA and GHRHRAA genotypes which were reported as desired genotypes for milk and growth production traits in different cattle breeds and the cattle are genetically homologous with buffaloes. To the best of our knowledge, these polymorphic sites are not identified in other buffalo populations. The identification of genotypes and nucleotide sequences of these two multifunctional genes may be useful in future marker-assisted selection (MAS) for more efficient breeding and genetic conservation programs of Egyptian buffalo.