Andrzej Maj

Nucleotide sequence and variation of IGF2 gene exon 6 in Bos taurus and Bos indicus cattle.

The major assumption of this study is that polymorphism of a gene could be used to investigate its allele-specific expression as well as its methylation and imprinting status. Therefore, the aim of this study was to analyze the polymorphism of the coding region of the bovine IGF2 gene and to determine the sequence of its gene exon 6 in Bos taurus and Bos indicus cattle. A single nucleotide “C” deletion/insertion polymorphism was found in both cattle subspecies and a G/T transversion (RFLP-MboII) in the Bos indicus IGF2 gene. A 407-bp fragment of bovine IGF2 exon 6 was sequenced and the sequences (including variable nucleotides) were deposited in the GenBank database. A comparative analysis was performed for this fragment from different species; 99.5% identity was found between Bos taurus and Bos indicus cattle.

Molecular evolution of coding and non-coding sequences of the growth hormone receptor (GHR) gene in the family Bovidae

The GHR gene exon 1A and exon 4 with fragments of its flanking introns were sequenced in twelve Bovidae species and the obtained sequences were aligned and analysed by the ClustalW method. In coding exon 4 only three interspecies differences were found, one of which had an effect on the amino-acid sequence--leucine 152 proline. The average mutation frequency in non-coding exon 1A was 10.5 per 100 bp, and was 4.6-fold higher than that in coding exon 4 (2.3 per 100 bp). The mutation frequency in intron sequences was similar to that in non-coding exon 1A (8.9 vs 10.5/100 bp). For non-coding exon 1A, the mutation levels were lower within than between the subfamilies Bovinae and Caprinae. Exon 4 was 100% identical within the genera Ovis, Capra, Bison, and Bos and 97.7% identical for Ovis moschatus, Ammotragus lervia and Bovinae species. The identity level of non-coding exon 1A of the GHR gene was 93.8% between species belonging to Bovinae and Caprinae. The average mutation rate was 0.2222/100 bp/MY and 0.0513/100 bp/MY for the Bovidae GHR gene exons 1A and 4, respectively. Thus, the GHR gene is well conserved in the Bovidae family. Also, in this study some novel intraspecies polymorphisms were found for cattle and sheep.

A LINE-1 element insertion in the 5'-noncoding region of caprine growth hormone receptor gene.

The GH receptor is a member of the cytokine/hematopoietin superfamily of receptors. The gene coding for GHR of most mammalian species consists of nine exons (numbered 2–10) in the translated part and a long 5′-noncoding region that includes several alternative untranslated exons, of which only exons 1A, 1B, and 1C have been studied in detail in the bovine GHR gene (Jiang and Lucy, 2001). Distinct promoters regulate transcription from each of the alternative exons. The P1 promoter, which drives growth hormone receptor expression in the liver, is associated with exon 1A in cattle and sheep (Jiang et al., 1999). A LINE-1 element from the family of retrotransposons, about 1.2 Kb long, was found upstream of bovine exon 1A (Lucy et al., 1998). This element was shown to be typical for European cattle and was absent from the Bos indicus GHR gene (Hale et al., 2000). In this study we sequenced 1269 bp of the caprine GHR gene 5′-noncoding region. A LINE-1 of 317 bp was found in this GHR gene fragment, which possibly represents a parallel and independent insertion event within homologous loci in the goat and cattle genome.