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M J Recio

Publications and source records attributed to M J Recio.

8 recordsLinked to original sources
PubMed1998

Phylogeny and rapid northern and southern hemisphere speciation of goldfinches during the Miocene and Pliocene epochs.

Mitochondrial cytochrome b (cyt b) from 25 out of 31 extant goldfinches, siskins, greenfinches and redpolls (genus Carduelis) has been sequenced from living samples taken around the world, specimens have also been photographed. Phylogenetic analysis consistently gave the same groups of birds, and this grouping was generally related to geographical proximity. It has been supposed that Pleistocene glaciations played a crucial role in the origin of extant diversity and distribution of Northern Hemisphere vertebrates. Molecular comparison of most extant songbird species belonging to the genus Carduelis does not support this assertion. The fossil record of chicken and pheasant divergence time has been used to calibrate the molecular clock; cyt b DNA dendrograms suggest that speciation in Carduelinae birds occurred during the Miocene and Pliocene Epochs (9-2 million years ago) in both the Northern and Southern Hemispheres. Only about 4% average amount of nucleotide substitution per lineage is found between the most distant Carduelis species; this suggests a remarkably rapid radiation when compared with the radiation of other passerine songbird genera. In addition, a continuum of small songbird speciation may be found during the Miocene Epoch in parallel with speciation of other orders (i.e. Galliformes, chicken/pheasant). Pleistocene glaciations may have been important in subspeciation (i.e. Eastern European grey-headed goldfinches/Western European black-headed goldfinches) and also in ice-induced vicariance (isolation) (i.e. siskin in Western Europe vs. siskin in Far East Asia) around the world. European isolated Serinus citrinella (citril finch) is not a canary, but a true goldfinch. South American siskins have quickly radiated in the last 4 million years coinciding with the emergence of the Isthmus of Panama; probably, a North American siskin related to C. notata invaded a suitable and varied biotope (the South American island) for Carduelis birds. North American goldfinches may be renamed as siskins, because they have a distant genetic relationship with European goldfinches. Genus Acanthis could be dropped, and thus redpolls should be separated from twite and linnet, the latter (Europeans) probably being related to American goldfinches. Also, reproductive barriers are observed between closely related species and not between other more distant ones. Finally, a tentative classification for genus Carduelis species is suggested.

Animals↗
PubMed1998

Transcription and weak expression of HLA-DRB6: a gene with anomalies in exon 1 and other regions.

HLA-DRB6 is one of the human major histocompatibility complex (MHC) genes present in DR1, DR2, and DR10 haplotypes (approximately 26% of individuals). It shows several anomalies in human and non-human primates, including exon 2 stop codons (non-randomly grouped between codons 74 and 94) and a promoter region, and an exon 1 coming from an inserted retrovirus. It has been shown that not only chimpanzee but also human Mhc-DRB6 lack the usual 3' untranslated (UT) polyadenylation signal, and in the present work it was found that the human DRB6 gene coming from an HLA-DR2 haplotype is effectively transcribed after transfection in mouse L cells, and that HLA-DRB6 molecules may be expressed on the cell surface. DRB6 transcription level is remarkably lower in human than in chimpanzee. Moreover, their exons 1 (both taken from the 3'LTR region of a mammary tumor retrovirus) are also different; this shows that these viral insertions may be an important mechanism for different evolutionary changes in orthologous genes of different species. The pathways by which DRB6 molecules may be expressed on the membrane are unclear but other examples of truncated protein expression have also been described, even within the human major histocompatibility complex (i. e., in HLA-G). Finally, the presence of mature HLA-DRB6 mRNA molecules supports the notion that splicing may take place even in the absence of a canonical 3'UT polyadenylation signal.

Amino Acid Sequence↗
PubMed1998

Description of two Mhc-C-related sequences in the New World monkey Saguinus oedipus.

Two new Mhc class I partial exon 1, intron 1, exon 2, intron 2 and partial exon 3 DNA sequences from the New World monkey Saguinus oedipus (Saoe) are described. These two sequences show certain Mhc-C sequence-specific changes. The only difference between these two new sequences is a productive substitution at position 152 [GCG (Ala)-->GAG (Glu)]. This change occurs in a position which in Mhc classical class I molecules affects the interaction between the peptide and the T-cell receptor. A dendrogram with Mhc sequences from different loci and different species was constructed, which clearly shows that these two new sequences cluster closer to Mhc-C sequences than to others. These data suggest that the new sequences may be related to the Mhc-C locus, and they have been named Mhc-Saoe-CR*01 and -CR*02. However, they share only a few of the conserved residues (from gorilla to human) of Mhc-C sequences, which suggests that the relationships with an ancestor of the Mhc-C lineage are very distant or that these two sequences are products of convergent evolution to perform a C locus related function. Furthermore, in the fragment of DNA sequenced, there is a loss of two invariant residues conserved in antigen-presenting molecules from reptiles to humans; thus, it is unlikely that these two Mhc-C-like sequences have an antigen-presenting function, or even that they are two alleles of a pseudogene; however, the G + C percentage (86.1%) at the third base of codons approaches that of an expressed gene in Saoe. It is concluded that Mhc molecules with C-locus characteristics existed in primates 50 million years ago and that this does not support a more recent origin of Mhc-C genes.

Alleles↗
PubMed1998

Allelic diversity at the primate MHC-DMB locus: presence of a conserved tyrosine inhibitory motif in the cytoplasmic tail.

Ten new primate Mhc-DMB complete cDNA sequences have been obtained in chimpanzee (n=four), gorilla (n=three) and orangutan (n=three); this gene has not been previously studied in these species. Exonic allelism has been recorded all along the molecule domains and also in the leader peptide, but not in the transmembrane segment. An analysis of the residues critical in the conformation of the Mhc-DR peptide-binding site was done in order to look for a Mhc-DR homologue site; synonymous substitutions are favoured in this homologous HLA-DM region. This is another finding that supports the possibility that DM could not be typically presenting molecules. The immunoreceptor inhibition motif Tyr 230-Thr/Ser 231-Pro 232-Leu 233 (ITIM) is invariantly present in apes for at least 15 million years, and may have a double function: 1) To direct DMB-DMA molecules from the endoplasmic reticulum or cell surface towards the endosomal/lysosomal class II compartment and 2) to send an inhibitory signal to the cell in order to stop synthesis of unnecessary HLA-DR molecules, once all available antigenic peptides are loaded. Other molecules, like NK-cell receptors and Fc receptors, bear this type of tyrosine-based inhibitory motifs in order to switch off specific cell functions. DMB molecules (as previously shown in C4d molecules) do not present species-specific motifs in common chimpanzee, suggesting that this species is very close to gorilla or man; also, DMB, like C4d molecules, do not show a trans-species evolution pattern, suggesting the existence of extensive homogenization of DMB genes within each species or a recent generation of alleles. Finally, a clade grouping human and gorilla DMB cDNA sequences is obtained using a dendrogram (as for C4d trees); this is in contrast to others' results that obtain a human/chimpanzee clade using different DNA sequences.

Alleles↗
PubMed1997

Mhc-E polymorphism in Pongidae primates: the same allele is found in two different species.

Mhc-E intron 1, exon 2, intron 2, and exon 3 from pygmy chimpanzee (Pan paniscus), chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus) have been sequenced; six new Mhc-E alleles have been obtained but sequence changes are only placed either in introns or in synonymous exonic bases. One pygmy chimpanzee Mhc-E DNA sequence is identical to another sequence from chimpanzee; the fact that no variation is found also at the intronic level suggests that these two species of chimpanzee may have recently separated and/or that both of them might only represent subspecies. Mhc-E phylogenetic trees separate two evolutionary groups: Pongidae, including humans, and Cercopithecinae; this is also found by studying another non-classical class I gene, Mhc-G. The Mhc-E alleles' invariance at the protein level supports that strong selective forces are operating at the Mhc-E locus, as has also been found in both Cercopithecinae and humans. These allelic and evolutionary data suggest an altogether different functionality for HLA-E (and also HLA-G) compared with classical class I proteins: i.e., sending negative (tolerogenic) signals to NK and T cells.

Alleles↗
PubMed1996

Allelic diversity at the primate Mhc-G locus: exon 3 bears stop codons in all Cercopithecinae sequences.

Twenty-seven major histocompatibility complex (Mhc)-G exon 2, exon 3, and exon 2 and 3 allelic sequences were obtained together with 12 different intron 2 sequences. Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis, Macaca mulatta, and Cercopithecus aethiops individuals were studied. Polymorphism does not follow the classical pattern of three hypervariable regions per domain and is found in all species studied; exon 3 (equivalent to the alpha 2 protein domain) shows stop codons in the Cercopithecinae group but not in the Pongidae and human groups. Dendrograms show that cotton top tamarin (Saguinus oedipus) Mhc-G sequences are closer to Homo sapiens and Pongidae than to Cercopithecinae, probably due to the stop codons existing at exon 3 of the latter. There is a clear trans-species evolution of allelism in Cercopithecinae and also in exon 2 of all the other apes studied, but a generation of allelism within each species may be present on exon 3 sequences. This discrepancy may be due to the preferential use of exon 2 over exon 3 at the mRNA splicing level within each species in order to obtain the appropriate functional G product. Mhc-G intron 2 shows conserved motifs in all species studied, particularly a 23 base pair deletion between positions 161 and 183 which is locus specific, and some of the invariant residues, important for peptide presentation, conserved in classical class I molecules from fish and reptiles to humans were not found in Mhc-G alleles; the intron 2 dendrogram also shows a particular pattern of allelism within each species. In summary, Mhc-G has substantial differences from other classical class I genes: polymorphism patterns, tissue distribution, gene structure, splicing variability, and probably an allelism variability within each species at exon 3. The G proteins may also be different. This indicates that the Mhc-G function may not be peptide presentation to the clonotypic T-cell receptor.

Alleles↗