Jean-Claude Mounolou

Rabbit Mitochondrial DNA Diversity from Prehistoric to Modern Times

The mitochondrial genetic variability in European rabbit (Oryctolagus cuniculus) populations present in Europe and North Africa from 11,000 years ago to the present day has been analyzed using ancient DNA techniques. DNA was extracted from 90 rabbit bones found in 22 archaeological sites dated between the Mesolithic and recent times. Nucleotide sequences present in a variable 233-bp domain of the cytochrome b gene were compared to those present in modern-day rabbits. The results show that the structure of ancient populations of wild rabbit exhibited remarkable stability over time until the Middle Ages. At this time, a novel type of mtDNA molecule abruptly appears into most wild populations studied from France. This mtDNA type corresponds to that currently present in the domestic breeds of rabbit examined so far. The relative rapidity by which this mtDNA type established and its absence in all sites examined before 1,700 years ago lend support to the hypothesis that between 2,000 and 1,000 years ago, man may have favored the development, into all regions of France, of animals carrying this particular mtDNA molecule. The origin of such animals has still to be found: animals previously living outside of France or within France but in very restricted areas? This event was concomitant with the documented establishment of warrens after the tenth century a.d. in Europe.

Mitochondrial Genes Collectively Suggest the Paraphyly of Crustacea with Respect to Insecta

Abstract. Complete sequences of seven protein coding genes from Penaeus notialis mitochondrial DNA were compared in base composition and codon usage with homologous genes from Artemia franciscana and four insects. The crustacean genes are significantly less A + T-rich than their counterpart in insects and the pattern of codon usage (ratio of G + C-rich versus A + T-rich codon) is less biased. A phylogenetic analysis using amino acid sequences of the seven corresponding polypeptides supports a sister-taxon status for mollusks–annelid and arthropods. Furthermore, a distance matrix-based tree and two most-parsimonious trees both suggest that crustaceans are paraphyletic with respect to insects. This is also supported by the inclusion of Panulirus argus COII (complete) and COI and COIII (partial) sequence data. From analysis of single and combined genes to infer phylogenies, it is observed that obtained from single genes are not well supported in most topologies cases and notably differ from that of the tree based on all seven genes.

Mitochondrial DNA: an advance in eukaryotic cell biology in the 1960s

Between 1950 and 1960 mitochondria were recognized as well‐characterized organelles of animal and fungal cells. They shared more functional autonomy than other cellular structures. The transmission of some mitochondrial characteristics did not obey Mendelian rules and followed cytoplasmic inheritance patterns. Was this situation a consequence of still unknown complexities? We present a personal account on how approaches were set up to test very different hypotheses. In the end, it was shown that mitochondria had their own DNA, mitochondrial DNA, and that this molecule carried information specific to these organelles.

Rabbit mitochondrial DNA: preliminary comparison between some domestic and wild animals

The map of the restriction endonuclease cleavage sites of rabbit mitochondrial DNA (mtDNA) has been established : 41 sites were mapped using 13 enzymes. This genome, although rather large for a mammalian mtDNA (17 300 bp), is organized in the typical vertebrate fashion. For each of 6 wild and 5 domestic rabbits belonging respectively to the subspecies Oryctolagus cuniculus algirus and Oryctolagus cuniculus cuniculus, mtDNA molecules are heterogeneous in size. The length variations of about 100 bp have been assigned to the main non coding region of the genome. Very curiously, according to these preliminary results the mtDNAs of the two subspecies exhibit similar restriction patterns. However, 2 variants were found among the animals examined, one in each population.

Heteroplasmy in the European rabbit: Mitochondria and mitochondrial DNA evolution through the germ line

In the Eurooean rabbit. Orvctolams cuniculrs. a svstematic heteroplasmy has been described wh&e every animal carl1es.a population of mitochondrial DNA (mtDNA) molecules differing in iheir length. Such an observation urged for the examination of&e evolution of these molecules and the organites which contain them, through generations. A genetic study, conducted on controled animal lineages (NeoCaledoman breed, INRA) has revealed that the transmission of mtDNA depends on three forces: drift, high level of mutations and selection which may vary according to the tissue and the age. A cytological analysis has been initiated, in parallel, to monitor the dynamics of mitochondria along the different steps of development. This work has been devoted, first, to the establishment of the germ line. Three days after birth, ovaries exhibit a vast majority of oogonia (SO%), the ram oocytes being at the beginning of meiotic prophase. At 40 days and further, all the germ cells are oocytes the nucleus of which is at diplotene and the cytoplasm in the growing phase. The ovaries from females (Neo-Caledonian breed) of different ages were taken out. The right ovary was fixed; the left one, incubated one hour in an enzymatic solution (D. Sz6lll)si pers. comm.), was dissected in order to isolate oogonia and oocytes for a genetic study. Ultrastructural examination of serial sections allowed the observation of whole germ cells. Skape, number and distribution of mitochondria were recorded according to the various stages (oogonia and oocytes). The results will be discussed in connection with the genetti analysis conclusions.