Biomedical subjects

Gustavo C S Kuhn

Publications and source records attributed to Gustavo C S Kuhn.

5 recordsLinked to original sources

PubMed2026

Retention of a single Cenp-C gene in different syntenic locations in the montium group of Drosophila species.

Chromosome segregation in eukaryotes requires the orchestrated interaction of chromosomes with microtubules, mediated by the kinetochore multiprotein complex that assembles on chromosomal regions known as centromeres. In most eukaryotes, CenH3 and Cenp-C centromeric proteins are essential for centromere function. In Drosophila, the localization of CenH3 (or Cid in Drosophila) depends on its chaperone CAL1 and Cenp-C. Previous studies have shown that both Cid and Cenp-C underwent a coincident gene duplication and likely functional specialization in the Drosophila subgenus. Independently, Cid duplications led to three paralogs in the montium group (Sophophora subgenus). Here, we investigated whether this group also underwent parallel Cenp-C duplications by analyzing sequenced genomes of 23 montium group species. We identified Cenp-C genes in five distinct syntenic loci. Despite their distinct synteny, all but two montium group species (except D. birchii and D. vulcana) encode a single Cenp-C, whose phylogeny mirrors the species phylogeny, and all encode protein motifs indicative of intact Cenp-C function. These Cenp-C genes resulted from gene translocations or duplication followed by loss of the ancestral copy. Therefore, the co-retention of three Cid paralogs in the montium group did not result in coincident Cenp-C paralog co-retention. Analysis of the selective constraints in Cenp-C reveals more prominent positive selection in the Drosophila subgenus (with two retained Cenp-C paralogs) than in the Sophophora subgenus, including the montium group. Our work highlights differences in functional retention and potential specialization of CenH3 and Cenp-C, two of the most conserved eukaryotic centromeric proteins in Drosophila.

Journal Article↗

PubMed2026

Satellite DNAs in Drosophila koepferae (repleta group) reveal patterns of origin, chromosomal organization, transcription, and turnover in the buzzatii cluster.

Satellite DNAs (satDNAs) are non-coding tandem repeats that can comprise more than 20% of eukaryotic genomes. They contribute to structural and regulatory processes in the genome and often evolve rapidly, shaping early stages of genetic differentiation between populations and species. Although Drosophila has long served as a model for studying satDNA biology, little is known about satDNAs in non-model Drosophila species, particularly within the repleta group, one of the most species-rich lineages in the genus. To reduce such bias, several studies have focused on the buzzatii cluster (repleta group). However, D. koepferae remained the only species lacking comprehensive satDNA data, limiting comparative analyses. Here, we used publicly available genomic sequencing data from two D. koepferae populations (Argentina and Bolivia) to characterize their satDNA content. Both populations share the same set of five satDNAs (CDSTR8, CDSTR138, CDSTR230, DBC-150 and CDSTR177), which together account for ~ 0,9% of the genomic DNA. We show that CDSTR177 originated through amplification of an internal segment of the Galileo transposable element, an event restricted to D. koepferae. All satDNAs localize to heterochromatic regions, with CDSTR138 most likely associated to the centromeres of most chromosomes. Transcripts from all satDNAs were detected, although at low levels. Our results provide new insights into the origin, genomic contribution, expression and evolution of satDNAs in the buzzatii cluster, support incipient differentiation between Argentinean and Bolivian populations of D. koepferae and contribute to clarifying the phylogenetic position of this species within the buzzatii cluster.

Animals↗

PubMed2005

Evolutionary turnover of two pBuM satellite DNA subfamilies in the Drosophila buzzatii species cluster (repleta group): from alpha to alpha/beta arrays.

The pBuM satellite DNA family was studied in seven Drosophila species from the buzzatii cluster (within the large Drosophila repleta group). The pBuM repeats are slightly AT-rich and show high levels of intraspecific sequence homogeneity. The pBuM family can be divided into two subfamilies. The pBuM-1 subfamily consists of tandemly arranged repetition units of approximately 190 bp, termed alpha. Alpha repeats were found in a high copy number in the genome of D. buzzatii, D. serido and D. antonietae. The pBuM-2 subfamily consists of tandemly arranged repetition units of 370 bp. Its origin is explained by an insertion of an approximately 180 bp foreign sequence (termed beta) in an alpha basic repeat unit, with subsequent homogenization/amplification events increasing its frequency. Alpha/beta repeats were found in a high copy number in the genome of D. serido, D. antonietae, D. seriema and D. gouveai. pBuM sequences were not detected in D. koepferae and D. borborema by hybridization experiments. The nucleotide analysis of 74 pBuM repeats revealed that apart from the beta insertion event, the evolution of the pBuM family has proceeded in a gradual fashion, mainly through accumulation and horizontal spread of nucleotide substitutions. Moreover, the data also indicate a faster evolutionary rate for the pBuM-2 subfamily than the pBuM-1 subfamily. Members of both subfamilies display a greater intraspecific than interspecific homogeneity, indicating a concerted mode of pBuM evolution. A scenario to explain the evolution of both satDNA subfamilies in the seven Drosophila species from the buzzatii cluster is proposed.

Animals↗

PubMed2004

Characterisation and interpopulation variability of a complex HpaI satellite DNA of Drosophila seriema (repleta group).

A HpaI satellite DNA has been isolated and characterised from the genome of Drosophila seriema, a cactus-breeding species endemic to the rock fields of the Espinhaço Range in Brazil. The monomer sequences are slightly A + T rich (66%) and there is a significant variation of repetition length (343-391 bp). The length variability is mainly due to a 22 bp indel in some repeats and the presence of a highly variable region characterised by several DNA rearrangements, including indels, inversions and duplications of small sequence segments. The retarded mobility of monomers observed after gel electrophoresis suggests DNA curvature. Thirty satDNA repeats were analysed in samples from five populations which cover D. seriema geographical distribution. Previous studies showed that these populations present low levels of chromosomal divergence in contrast to high levels of mtDNA divergence. The variability among the 30 repeats is pretty low, on average 2%. The results showed that the satDNA sequences are rather homogeneous on both intra and interpopulational levels, presenting no specific feature(s) that could discriminate a particular population or groups of geographically close populations. Possible factors responsible for such homogeneity are discussed.

Animals↗

PubMed2003

On the pBuM189 satellite DNA variability among South American populations of Drosophila buzzatii.

The pBuM189 satellite DNA was analysed in Drosophila buzzatii populations that cover most of the species distribution in South America. This satDNA consists of A + T-rich monomers of 189 bp and previous studies showed a fast rate of evolutionary change of this component of D. buzzatii genome. A total of 63 pBuM189 repetition units from 14 D. buzzatii populations (9 from Brazil and 5 from Argentina) were studied. The average nucleotide variability among the 63 repeats is 4.2 %. At least one repeat (Juan/4) seems to be part of another pBuM189 satDNA subfamily. The nucleotide alignment of all 63 repeats revealed no specific nucleotide substitutions, or indels, that could discriminate each population or groups of geographically close populations. Such lack of satDNA interpopulational differentiation is congruent with previous mtDNA data that indicate a high gene flow and very little population differentiation throughout most of the D. buzzatii distribution in South America. Gene flow might have been possible during glaciation events in the Pleistocene, such as the one occurred between 13,000 and 18,000 years ago, when D. buzzatii probably had a more continuous distribution than what is observed today.

Animals↗