RESUMO
BACKGROUND: CD29 is the beta1 subunit, a member of the integrin gene superfamily that function as receptor for cell adhesion molecules of the extracellular matrix. Porcine integrin beta1 subunit is involved in rejection of pig-to-human tissue xenografts as target of the natural antibodies present in the human serum. Moreover since CD29, as part of the beta1 integrins very late antigen 4 (VLA-4) and VLA-6, is involved in homing and differentiation of haematopoietic progenitor cells, its characterization in pig is critical to study the interaction of porcine adhesion molecules with human ligands in the induction of donor-specific tolerance toward porcine antigens, a process extremely desirable to prevent rejection of xenogeneic organs. METHODS: The porcine CD29 cDNA has been isolated from a cDNA library and its structure determined. In addition, reverse transcription-polymerase chain reaction (RT-PCR) was performed to determine the expression of CD29 in different tissues. RESULTS: The nucleotide sequence of the porcine cDNA includes an open reading frame encoding a polypeptide of 798 amino acids. Expression analysis showed that porcine CD29 is expressed in all lymphoid tissues tested and, in lower amounts, in nonlymphoid tissues. Pig CD29 deduced amino acid sequence displays extensive conservation compared with CD29 sequences from other species and a common structural feature with all the other CD29 molecules analyzed in mammals, including the 12 potential N-glycosilation sites. Punctual changes between human and swine CD29 molecule into the ligand binding domain, and/or into the regulatory domain, suggest potential differences between human and porcine CD29 relative to the human CD29 ligands. CONCLUSIONS: Cloning of the swine CD29 gene offers a new tool for an alternative protocol of removing xenoreactive antibodies in the recipient. In addition, the determination of the differences between human and swine CD29 will help to understand the adhesion molecule-ligand interactions and their function across the swine-human barrier in xenotransplantation.
Assuntos
Antígenos CD/genética , Integrina beta1/genética , Sequência de Aminoácidos , Animais , Antígenos CD/química , Sequência de Bases , Gatos , Galinhas , Clonagem Molecular , Biblioteca Gênica , Humanos , Integrina beta1/química , Camundongos , Dados de Sequência Molecular , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Suínos , Xenopus laevisRESUMO
A swine genomic cosmid library constructed from a genotypically SLA homozygous Large White individual was screened with a murine genomic 21-hydroxylase probe. A clone which contained a pig 21-hydroxylase gene was isolated and after subcloning, the 5' region of the gene was sequenced. The deduced amino acid sequence corresponded almost exactly to the NH2 terminal portion of the steroid 21-hydroxylase from porcine adrenal microsomes. Comparison of the first 99 amino acid residues of both sequences revealed three substitutions comprising two leucine residues in positions 10 and 13, and one arginine residue in position 55 for our sequence, instead of threonine in position 10 and lysine in position 13 and 55 for the isolated enzyme. A swine homologous probe was derived from the isolated 21-hydroxylase gene and used for gene assignment by RFLP studies in two swine leucocyte antigen (SLA) informative families. The results demonstrate that the swine 21-hydroxylase gene is located within or close to the swine MHC. Taken together, the present results suggest the existence of a single 21-hydroxylase gene per haploid genome.
Assuntos
Antígenos de Histocompatibilidade/genética , Esteroide 21-Hidroxilase/genética , Esteroide Hidroxilases/genética , Suínos/genética , Animais , Sequência de Bases , Clonagem Molecular , DNA/genética , Feminino , Biblioteca Gênica , Genes MHC Classe I , Masculino , Dados de Sequência Molecular , Mapeamento por Restrição , Suínos/imunologia , Suínos/metabolismoRESUMO
A study, by means of computer simulation, has been performed on the evolution of recombination rate modifier genes in a system with three diallelic loci (A, B and C). The locus C, selectively neutral, is responsible for the modification of the recombination fraction between the major loci (A and B) which are subjected to selection. Two models have been analysed, the modifier allele being recessive in one of them, and codominant in the other, with infinite and finite populations. Distinct initial genic frequencies of the major loci and different selection coefficients have been utilised. We have found that the frequency of the allele which favours recombination increases in finite populations, and decreases slightly in infinite populations. These results are consistent with previous theory; presumably, selection favours alleles reducing recombination between epistatically interacting loci in a infinite population, since this reduces the breakup of advantageous combinations of alleles. However, in finite populations, selection favours the breakup of the random linkage disequilibria which are produced by random drift.
Assuntos
Evolução Biológica , Simulação por Computador , Modelos Genéticos , Recombinação Genética , Mapeamento Cromossômico , Frequência do Gene , Genes , Genes DominantesRESUMO
Genetic variants at eight blood loci were analysed, disclosing in Andalusian breed six rare markers: variants J of transferrin, H of esterase, D and S of Xk, M and W of prealbumin. Two of these, TfJ and PrM appear as characteristic markers of Andalusian breed. Allelic frequencies showed minor differences between Spanish (300 horses) and Lusitanian (100 horses) populations. Comparison was established with historically related breeds, Thoroughbreds or Connemara, and with Arab horses because of a presumed relationship. No visible similarities in genetic profiles were found with two former breeds, nor with Arab horses. Unpredicted similarities were found however between Tarpans and Andalusian horses, appearing rather as convergences than witnessing a common ancestry.
