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M Hauwy

Publications and source records attributed to M Hauwy.

7 recordsLinked to original sources

Application of molecular cytogenetics for chromosomal evolution of the Lemuriformes (Prosimians).

R-banding chromosomal studies of 21 species of Lemuriformes allowed us to reconstruct the presumed ancestral karyotype of all the Lemuriformes except for Daubentoniidae and permitted the construction of their phylogenetic tree. Chromosome painting with fluorescently labeled heterologous DNA probes permitted comparative chromosome maps to be established. The Zoo-FISH method was used to reassess the karyotypes of 22 species or subspecies. While our results largely confirm the previous reconstruction of the ancestral karyotype, they resulted in a modification of the previously established phylogenetic tree. The Daubentoniidae emerged first followed by the divergence of the families Cheirogaleidae, Indriidae, Lepilemuridae and Lemuridae. Eight chromosome rearrangements occurred in all Lemuriformes except for Daubentoniidae in the common trunk. The present findings do not allow us to propose the occurrence of any rearrangement common to Daubentoniidae and other Lemuriformes, and probably other Prosimii. Conserved syntenies previously described in various mammalian orders were also conserved, while others were specific to the Lemuriformes.

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Transposition of SRY into the ancestral pseudoautosomal region creates a new pseudoautosomal boundary in a progenitor of simian primates.

We have isolated the prosimian lemur homologues for STS and SRY. FISH unambiguously co-localized STS with SHOX, IL3RA, ANT3 and PRK into the meiotic X-Y pairing region (PAR) of lemurs. In contrast to the close proximity of SRY to the pseudoautosomal boundary (PAB) on the Y chromosome in simian primates, SRY maps distant from the PAR in lemurs. Most interestingly, we were able to determine a DNA sequence divergence of 12.5% between the human and lemur SRY HMG box. This divergence directs to a 52 million year period of separate evolution of human and lemur SRY genes. Phylogenetically, this time period falls in between the times that prosimians and New World monkeys branched from the human lineage. Thus, we conclude that approximately 52 million years ago a transposition of SRY into the ancestral eutherian PAR distal to STS and PRK defined a new PAB in a simian progenitor. By this event, STS and PRK, amongst other genes, were excluded from the X-Y crossover process and thus became susceptible to rearrangements and/or deterioration on the Y chromosome in simian primates.

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Chromosome painting: a method for testing chromosomal changes in lemur evolution.

Chromosome painting using commercially available human chromosome-specific DNA libraries was performed to elucidate chromosomal rearrangements in lemur evolution. Human-specific probes for chromosomes 3, 14, 15, and 21 were used to paint chromosomes of six species: Eulemur fulvus mayottensis, Varecia variegata, Lemur catta, Hapalemur simus, H. griseus griseus, and H. aureus. All human chromosome libraries hybridized specifically to chromosome segments of varying length or to whole arms of Lemur chromosomes. The labeling was clearly visualized and permitted precise delineation of the hybridized Lemur chromosomal segments. The use of commercial probes of human chromosomes for chromosome painting appears efficient enough to investigate homology in different species of Lemur. In general, the results obtained by chromosome painting in this study confirm results previously obtained by the R-banding technique but modify the location of some chromosomal rearrangements on different branches of the evolutionary tree of the Lemuridae and reveal some new rearrangements that were not detectable with banding techniques. These results show that chromosome painting with human chromosome-specific DNA libraries can provide useful information in comparative studies on karyotypes of distantly related mammalian species, providing a powerful tool for evolutionary studies, especially in phylogeny.

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Cytogenetic study of Hapalemur aureus.

The karyotype of Hapalemur aureus was compared with those of other Hapalemur species, allowing us to determine the phylogenetic position of this species on the evolutionary tree of the Lemuridae.

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Cytogenetic arguments in favour of a taxonomic revision of Lepilemur septentrionalis.

Cytogenetic investigations performed on 30 specimens of Lepilemur septentrionalis confirmed the existence of 4 karyotypes differing from each other by 1-2 chromosomal rearrangements. These data, pooled with those obtained in earlier studies, showed that out of 60 animals karyotyped only two kinds of hybrids were detected, allowing us to characterise two chromosomally polymorphic populations. No natural hybrids could be found between these two populations, which could thus be considered as two separate species. The possible role of the chromosomal rearrangements in the process of reproductive isolation between these two populations is discussed.

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