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R Montiel

Publications and source records attributed to R Montiel.

7 recordsLinked to original sources
PubMed2005

Population genetics of wild-type CAG repeats in the Machado-Joseph disease gene in Portugal.

OBJECTIVE: To gain insights on the molecular mechanisms of mutation that led to the emergence of expanded alleles in the MJD gene, by studying the behavior of wild-type alleles and testing the association of its distribution with the representation of the disease. METHODS: The number of CAG motifs in the MJD gene was determined in a representative sample of 1000 unrelated individuals. Associations between the repeat size and the epidemiological representation of MJD were tested. RESULTS: The allelic profile of the total sample was in the normal range (13-41 repeats), with mode (CAG)23. No intermediate alleles were present. Allelic size distribution showed a negative skew. The correlation between the epidemiological representation of MJD in each district and the frequency of small, medium and large normal alleles was not significant. Further correlations performed grouping the districts also failed to produce significant results. CONCLUSIONS: The absence of association between the size of the repeats and the representation of MJD demonstrates that prevalence is not an indirect reflection of the frequency of large normal alleles. Globally the results obtained are in accordance with a model that postulates the occurrence of a few mutations on the basis of most of the MJD cases worldwide.

Ataxin-3↗
PubMed2005

Occurrence and characterization of a nucleopolyhedrovirus from Spodoptera littoralis (Lepidoptera: Noctuidae) isolated in the azores.

A nucleopolyhedrovirus (SpliMNPV-Az) was isolated from diseased larvae of Spodoptera littoralis, collected at the Island of S. Miguel in Azores. The virulence of this isolate was tested against S. littoralis larvae in laboratory. LD50 against 2nd and 3rd instars were not significantly different, 1.44x10(4), 3.89x10(4) OBs per larvae, respectively, but both were significantly different from that against 4th instar, which was 61.3x10(4) OBs per larvae. The complete codons sequence of SpliMNPV-Az Polh gene obtained was 750 bp (NCBI GenBank Accession No. AY600451). This sequence was compared to other 38 polyhedrin genes from NPVs and to 6 granulin genes from GVs and resulted to be identical to the sequence of a SpliMNPV previously published, thus indicating that the natural host of SpliMNPV-Az must be S. littoralis. Genetic distances estimated from restriction enzymes profiles showed SpliMNPV-Az is close to the Egyptian SpliMNPV type B, despite some degree of genetic divergence suggested by slight differences observed on PstI profile.

Amino Acid Sequence↗
PubMed2005

Analysis of Y-chromosome variability and its comparison with mtDNA variability reveals different demographic histories between islands in the Azores Archipelago (Portugal).

We determined the Y-chromosomal composition of the population of the Azores Islands (Portugal), by analyzing 20 binary polymorphisms located in the non-recombining portion of the Y-chromosome (NRY), in 185 unrelated individuals from the three groups of islands forming the Archipelago (Eastern, Central and Western). Similar to that described for other Portuguese samples, the most frequent haplogroups were R1(xR1b3f) (55.1%), E(xE3a) (13%) and J (8.6%). Principal components analysis revealed a Western European profile for the Azorean population. No significant differences between Azores and mainland Portugal were observed. However, the haplogroup distribution across the three groups of islands was not similar (P<0.003). The Western group presented differences in the frequencies of haplogroups R1, E(xE3a) and I1b2 (27.3%, 22.7% and 13.6%, respectively) when compared to the other two groups. An assessment of the NRY variability, and its comparison with mitochondrial DNA (mtDNA) variability, was further evidence of the differential composition of males during the settlement of the three groups of islands, contrary to what has been previously deduced for the female settlers using mtDNA data.

Base Sequence↗
PubMed2003

Genetic structure and origin of peopling in the Azores islands (Portugal): the view from mtDNA.

The Azores islands (Portugal), uninhabited when discovered by Portuguese navigators in the fifteenth century, are located in the Atlantic Ocean 1500 km from the European mainland. The archipelago is formed by nine islands of volcanic origin that define three geographical groups: Eastern (S. Miguel and Sta. Maria), Central (Terceira, Faial, Pico, Graciosa and S. Jorge) and Western (Flores and Corvo). To improve the genetic characterisation of the Azorean population, and to clarify some aspects related to the history of settlement, a study of mtDNA was conducted in the population of the archipelago. The HVRI region was sequenced and specific RFLPs were screened in 146 samples obtained from unrelated individuals with Azorean ancestry (50 from the Eastern group, 60 from the Central group, and 37 from the Western group). Samples were classified into haplogroups based on the information obtained from both sequencing and RFLP analysis. All the analyses performed support the idea that, in the whole group of islands, the majority of mtDNA lineages originated from the Iberian Peninsula, mainly from Portugal (mainland). However contributions from other European populations, especially from Northern Europe, cannot be disregarded. The values obtained for the various diversity parameters in the Azores archipelago indicate that the Azorean population, as a whole, does not exhibit the typical characteristics of an isolated population. The analysis of genetic data by groups of islands showed that the Western group exhibited particular features. The distribution of haplogroups in the Western group is very atypical, being significantly different from what is observed in the Eastern and Central groups. Furthermore, the diversity values are, in general, lower than those observed in other populations used for comparison. African haplogroups were found in all the groups of islands. Therefore the presence of Moorish and African slaves on the islands, as reported in historical sources, is supported by the mtDNA genetic data, especially in the Eastern group. The presence of Jews in the Central group is also supported by the mtDNA data. Neither historical nor genetic data (phylogeography of mtDNA) supports the idea of a differential settlement history for the Western group; however, it is represented in the phylogenies as an isolated branch. The effect of genetic drift, induced by the reduced population size since peopling occurred, has led to a very atypical distribution of haplogroups/haplotypes in this group of islands. We cannot ignore the influence of biodemographic and genetic processes, namely founder effect, genetic drift, migration, and even recent mutational events in the mtDNA lineages of the Azorean populations. Nevertheless, a great part of the variation in the Azorean mtDNA can be explained by the settlement history.

Azores↗
PubMed2001

Authenticating ancient human mitochondrial DNA.

The use of ancient DNA techniques in human studies has been hampered by problems of contamination with modern human DNA. The main problem has been that the object of study belongs to the same species as the observer, and the complete elimination of the contamination risk is seemingly unlikely. Contamination has even been detected in the most specialized laboratories in this field. In these kinds of studies it is therefore very important to detect contamination and to distinguish contaminants from authentic results. Here, we report the use of a strategy to authenticate the identity of ancient mitochondrial DNA (mtDNA), based on the previously established relationship between D-loop sequence substitutions and haplogroup-specific restriction site changes. Forty-four individuals from a 16th-century necropolis were analyzed, from which 28 control region sequences were obtained. These sequences were preclassified into haplogroups, according to the observed motifs. Subsequently, the DNA extracts from which the sequences were obtained, along with independent extracts of subsets of the same individuals, were subjected to restriction fragment length polymorphism (RFLP) analysis to compare and corroborate the results. Using this approach, 24 sequences were authenticated, while two were discarded because of result mismatches. The final distribution of the haplogroups in the sample, and the differences in the sequences, are two additional criteria of authentication.

Adult↗