Biomedical subjects

Renato Robledo

Publications and source records attributed to Renato Robledo.

6 recordsLinked to original sources

PubMed2006

Further data on a 9.1-kb insertion-deletion polymorphism: survey of Mediterranean populations.

We report the distribution of a previously described 9.1-kb insertion-deletion polymorphism located on chromosome 22. We analyzed 1,844 individuals sampled from 26 Mediterranean populations in mainland Italy, Sicily, Sardinia, Tunisia, Libya, Morocco, Egypt, Greece, and Albania. The 9.1 kb - allele is the prevalent allele in the North African (range, 0.53-0.56), Greek (0.51), and Albanian (0.66) populations, whereas the 9.1 kb + allele is most frequent in a mainland Italian town (0.55) and in all Sicilian and Sardinian towns and villages thus far tested, with marked fluctuation ranges of 0.53-0.78 and 0.56-0.80, respectively. In tests for Hardy-Weinberg equilibrium the genotype frequencies observed in Athens and in four of the nine towns in Sicily (but in none of the towns in Sardinia) departed highly significantly from the expected values. Identical results were found in the same towns for a second insertion-deletion polymorphism located on chromosome 22ql13 at a distance compatible with a low incidence of recombination. The data, which are in good agreement with the different histories of the two islands (Sardinia and Sicily), are consistent with a west-east differentiation in Sicily and support the evidence for ancient gene flow from the Iberian peninsula to Sardinia.

Africa, Northern↗

PubMed2005

TaqMan genotyping of insertion/deletion polymorphisms.

The 5' fluorogenic (TaqMan) assay has been successfully used in screening for single-nucleotide polymorphisms; the very few steps required and the ability to automate each step allow for high-throughput screening. Insertion/deletion polymorphisms are an important class of markers that can be studied for different applications, such as diagnostics, genome variation, and species identification. Polymerase chain reaction (PCR) and post-PCR analysis are required to score the insertion or the deletion allele. In this chapter, we describe an expansion of the TaqMan technology for a rapid, high-throughput, screening for insertion/deletion polymorphisms in which the exact endpoints are known. The method requires minimal post-PCR analysis and can be applied to polymorphisms of any size.

Alleles↗

PubMed2004

The immunoglobulin lambda variable light-chain region in primates has been shaped by multiple, independent, small-scale and large-scale insertion/deletion events.

We analyzed genomes of nonhuman primates to determine the ancestral state of a 9.1-kb insertion/deletion polymorphism, located on human chromosome 22. The 9.1-kb+ allele was found in 16 chimpanzees, 3 bonobos, and 2 Bornean orangutans; however, 9 chimpanzees and 6 Sumatran orangutans showed neither the 9.1-kb+ nor the 9.1-kb- allele, but a novel allele, termed 9.1-kbnull. A clone from a chimpanzee BAC library carrying the 9.1-kbnull allele was sequenced: the BAC DNA aligns with the human chromosome 22 reference sequence except for a 75-kb region, suggesting that the 9.1-kbnull allele originated from a deletion. Furthermore, the 9.1-kb+ chromosomes of chimpanzees and bonobos contain a 1030-nucleotide sequence, absent in humans, that may result from a retro-transposition insertion in their common ancestor. Our results provide additional evidence that human chromosome 22 has undergone multiple small-scale and large-scale insertions and deletions since sharing a common ancestor with other primates.

Animals↗

PubMed2003

A simple and cost-effective method for rapid genotyping of insertion/deletion polymorphisms.

We developed a simple method, based on the TaqMan technology, for fast genotyping of insertion/deletion polymorphisms of known location. The genotypes of 22 CEPH individuals, previously ascertained by conventional methods, were confirmed in the new assay without manual, time-consuming, post-PCR analysis. We propose to expand the application of TaqMan probes for population screening of insertion/deletion polymorphisms in which the exact endpoints of the insertion/deletion are known. The method can be applied to polymorphisms of any size and can be used for different applications such as diagnostics, genome variation, and species identification.

Alleles↗

PubMed2003

A 9.1-kb insertion/deletion polymorphism suggests a common pattern of genetic diversity in Island Melanesia.

Earlier reports suggest a distinct pattern of genetic variation linked to both language and geographic distance in Island Melanesia. Inland Papuan-speaking populations from different islands tend to share one allelic profile, while shore-based or more cosmopolitan populations share another, related to Southeast Asian influence over the past 3000 years. In the present paper, we report the genotypes and allele frequencies of an informative 9.1-thousand-base-pairs (kb) insertion/deletion polymorphism in 19 populations living in Island Melanesia. The populations studied inhabit the islands of New Britain, New Ireland, New Hanover, and Mussau in the Bismarck Archipelago, and speak either Austronesian or Papuan languages. We also include for reference a collection from New Guinea and Bougainville. The data show a marked fluctuation in the allele frequency among the different isolates, with the 9.1-kb(-) allele frequency ranging from 0.67 to 0.98. The deletion allele reaches fixation in some Papuan-speaking interior populations of New Britain, as well as in the interiors of New Guinea and Bougainville. However, certain inland Austronesian-speaking populations also share a similar high frequency of the deletion. Our data suggest that language distinctions are generally, but not invariably, indicative of diverse allelic patterns in this complex region, where inland groups on large islands tend to be often distinctive from shore-based populations.

Gene Deletion↗

PubMed2002

A 9.1-kb gap in the genome reference map is shown to be a stable deletion/insertion polymorphism of ancestral origin.

We show a mute 9.1-kb gap in the human genome reference map, unraveled by RDA studies, to be a worldwide deletion/insertion polymorphism of stable type. The molecular and population data presented suggest its origin from a unique ancestral transposition event in chromosomal region 22q11.2, overlapping the IglambdaV genes at about 450 kb from the cluster of the IglambdaJ-C genes. These findings are not meant to be just another report of a polymorphic marker suitable for population studies. Rather, we wish to stress that a large number of inborn mute gaps may be spread all over the genome and that the many RDA-detected microdeletions already available are efficient tools for the discovery of this otherwise hidden category of genetic variation. Apart from their possible impact on expression of structural genes, mute gaps must be filled for the reference map of our genome to be truly completed.

Chromosome Deletion↗