Non-existence of HinfI polymorphism in exon 6 of Pit-1 gene in “Serra da
Estrela” and “Merino da Beira Baixa” Portuguese ovine dairy breeds.
Marques, M. R.*, Santos, I. C.*, Belo, C. C.*, Cravador, A.**
*Departamento de Ovinicultura e Caprinicultura,
Estação Zootécnica Nacional,
Fonte Boa, 2000-763 Vale de Santarém, Portugal.
tel 243767300 e-mail: [email protected]
**
Unidade de Ciências e Tecnologias Agrárias,
Universidade do Algarve,
Campus de Gambelas, 8000-810 Faro, Portugal.
e-mail: [email protected]
Abstract
Pit-1 is a pituitary specific transcription factor responsible for regulation of
expression of growth hormone (GH), prolactin (PRL) and thyrotropine in mammals.
Woollard et al. (1994) found a mutation that suppresses a HinfI restriction site located
in exon 6 of bovine Pit-1 gene detectable by restriction fragment length polymorphism
(RFLP). This technique allowed the detection of allele A (HinfI restriction site absent)
and B (HinfI restriction site present). These alleles give three genotypes: AA, AB and
BB. The presence of allele A has been associated to high milk and protein yield, and
low fat content (Renaville et al., 1997). The authors also referred that genotype AB is
significantly better for milk and protein yield than genotype BB.
The objective of this study was to determine whether these genotypes exist in
ovine species, namely in “Serra da Estrela” and “Merino da Beira Baixa” ovine dairy
breeds and if so, to correlate them with productive parameters. We looked for the
existence of this HinfI-RFLP polymorphism in 100 animals of each of these Portuguese
breeds.
A fragment of 241 bp of the exon 6 of Pit-I gene was amplified by polymerase
chain reaction (PCR) and digested with restriction enzyme HinfI. The restriction
product was analysed by agarose gel electrophoresis. Two fragments of 196 bp and 45
bp were detected in all the 200 animals analysed, demonstrating the presence of HinfI
restriction site corresponding to BB genotype. These results suggest that contrary to the
claim presented by Renaville (1998), the allele A could be absent in ovine species.
References: Renaville, R. et al. (1997), J. Dairy Sci., 80:3431-3438
Renaville, R. Portetelle, D. (1998), European Patent Office, EP 0 821 070
A1
Woollard, J. et al. (1994), J. Anim. Sci., 72:3267
Key words: Ovine, Pit-1, HinfI-RFLP, polymorphism, milk yield
This work was supported by PRAXIS XXI (Project 3/3.2/CA/1991/95).