Cécile Arnould

A detailed analysis of the MECP2 gene: prevalence of recurrent mutations and gross DNA rearrangements in Rett syndrome patients

Abstract. Mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2) have been found to be a cause of Rett syndrome (RTT). In order to provide further insights into the distribution and the spectrum of mutations, we investigated, in addition to the whole coding sequence, a phylogenetically conserved sequence within the 3 untranslated region (3 UTR) of the MECP2 gene for 55 sporadic RTT, including 47 typical and 8 nonclassical cases. We have developed an approach based on conformation-sensitive gel electrophoresis, sequence analysis and, for the first time, Southern blot analysis. Mutation detection, including unreported gross DNA rearrangements, was achieved in 79% of classical RTT and 25% of nonclassical RTT patients. The high prevalence of recurrent mutations allows us to propose a molecular diagnosis strategy for RTT.

Retention of individual recognition in chicks and the effects of social experience

Young domestic fowl chicks, Gallus gallus domesticus, discriminate between familiar and unfamiliar agemates. We investigated the retention of individual discrimination and the effects of social experience on such recognition memory. In the first series of experiments, chicks were paired with an initial social partner (I) for 22.5 or 42xa0h. These I pairs were then separated and each chick was housed with a new partner (Recent: R) for about 19xa0h. During subsequent tests, interactions between I partners did not differ from those of unfamiliar test pairs. However, chicks in R pairs pecked at their partners less frequently during the test trials and spent more time in physical contact than did unfamiliar pairs. Chicks in two additional experiments were similarly housed in pairs with an initial partner, then either isolated or housed with a new partner in an unlit room. After these treatment procedures, chicks in both experiments pecked at lower frequencies when tested with their I partner compared to an unfamiliar agemate. We conclude that retention of a memory trace of a social partner depends upon the chicks intervening experience during the separation period. Exposure to a second individual interferes with the recognition memory of the first partner. Furthermore, the negative effect of the second partner on the retention of a memory trace of a previous partner depends on familiarization with the second partners visual phenotype.

The temporal development and sensory mediation of social discrimination in domestic chicks

We conducted a series of experiments to investigate the temporal development and sensory basis of social discrimination by young chicks, Gallus gallus domesticus . In the initial experiment, 1-day-old chicks were housed in pairs for 6–9 or 11–14xa0h. After this treatment period, interactions between paired chicks that had been housed together for 6–9xa0h did not differ from those of unfamiliar chicks. However, pairs of chicks that had been together for 11–14xa0h pecked each other significantly less than did unfamiliar pairs. Reduced pecking by the familiar partners indicates that 11–14xa0h of direct contact is sufficient for the establishment of individual discrimination. In a second experiment we assessed the role of olfaction in the development of social discrimination. Chicks in the anosmic condition were housed in pairs after their external nares were blocked with acrylic cement. Control chicks had cement applied to the beak (the nares remained uncovered) before being housed in pairs. When tested after the pair-housing period, pecking frequencies were lower among familiar cagemates than among unfamiliar pairs of chicks in both the anosmic and control conditions. Anosmic chicks, unlike the controls, showed little reaction to mint odour, thereby verifying that the blocked-nares treatment disrupted olfactory perception. In a final experiment, there was no reliable difference between the pecking rates of paired chicks that had been housed together in the dark and those of unfamiliar dark-reared pairs. We conclude that access to social partners visual phenotype, but not olfactory familiarization, is necessary for the rapid development of individual discrimination by chicks.

Motivation to dust-bathe of laying hens housed in cages and in aviaries.

New housing systems for commercial egg production, furnished cages and non-cage systems, should improve the welfare of laying hens. In particular, thanks to the presence of a litter area, these new housing systems are thought to satisfy the dust-bathing motivation of hens more than in conventional cages, in which no litter area is present. However, although apparently obvious, there is no concrete evidence that non-cage systems, particularly aviaries, satisfy hens motivation to dust-bathe and thus improve hens welfare in terms of dust-bathing behaviour. The aim of this study was to compare hens dust-bathing motivation when housed for a long time under similar conditions to commercial conditions in laying aviaries (with litter) and in conventional cages (without litter). Three treatments were compared: hens reared in floor pens then housed in conventional cages, hens reared in furnished floor pens then housed in a laying aviary, and hens reared in rearing aviaries then housed in a laying aviary. All three treatments provided access to litter during the rearing period. After transfer to the laying systems, access to litter was maintained for the aviary hens but stopped for the cage hens. Twelve groups of four hens per treatment were tested 36 to 43 weeks after transfer. The hens were placed in sawdust-filled testing arenas, and latency to dust-bathe, duration and number of dust baths, and number of hens dust-bathing were recorded. Latency to dust-bathe was shorter, dust baths were longer and more numerous and more hens dust-bathed among cage hens than among aviary hens. Our results indicate that hens motivation to dust-bathe was more satisfied in laying aviaries than in conventional cages. Thus, laying aviaries improve hens welfare in term of dust-bathing behaviour compared with conventional cages.

Artificially Increased Yolk Hormone Levels and Neophobia in Domestic Chicks

In birds there is compelling evidence that the development and expression of behavior is affected by maternal factors, particularly via variation in yolk hormone concentrations of maternal origin. In the present study we tested whether variation in yolk hormone levels lead to variation in the expression of neophobia in young domestic chicks. Understanding how the prenatal environment could predispose chicks to express fear-related behaviors is essential in order to propose preventive actions and improve animal welfare. We simulated the consequences of a maternal stress by experimentally enhancing yolk progesterone, testosterone and estradiol concentrations in hen eggs prior to incubation. The chicks from these hormone-treated eggs (H) and from sham embryos (C) that received the vehicle-only were exposed to novel food, novel object and novel environment tests. H chicks approached a novel object significantly faster and were significantly more active in a novel environment than controls, suggesting less fearfulness. Conversely, no effect of the treatment was found in food neophobia tests. Our study highlights a developmental influence of yolk hormones on a specific aspect of neophobia. The results suggest that increased yolk hormone levels modulate specifically the probability of exploring novel environments or novel objects in the environment.

Individual discrimination following 24 h of pair contact in one- and seven-day-old Japanese quail ( Coturnix japonica )

Summary This study examined the capacity of young Japanese quail to discriminate between a familiar cagemate (F) and an unfamiliar conspecific (U). Two tests of discrimination were initially compared: a simultaneous double choice test and a pair test allowing social pecking. Discrimination was more clearly demonstrated in the choice test, which was, therefore, used in the subsequent experiments. One-day-old chicks that had been housed in pairs after hatching spent significantly more time near F than a U stimulus bird and more frequently approached and attempted to interact with F. Seven-day-old chicks that were raised in large groups for the first 6 days, then in pairs for 24 h, subsequently displayed no significant differences in their responses to their recent pair partner versus an unfamiliar chick. On the other hand, chicks that were raised in pairs for 6 days, then housed with a new partner (F) for 24 h, more frequently approached and attempted to interact with F than a U bird. These results show that 24 h of pair contact beginning at hatching or 6 days of age is sufficient for quail to discriminate between a familiar cagemate and a stranger. This discrimination ability is influenced by the chicks early social experience.

La microdissection chromosomique ou le paradigme de la cytogénétique moléculaire : de la caractérisation des anomalies chromosomiques complexes à l'identification de gènes

La microdissection chromosomique est une technique de cytogenetique moleculaire tres performante dans lanalyse des aberrations chromosomiques complexes associees aux malformations congenitales, aux affections accompagnees dun retard mental ou observees au cours des cancers. Elle occupe, en outre, une place a part entiere dans le domaine de la recherche en genetique chromosomique et tout particulierement dans la cartographie physique du genome et lisolement de nouveaux genes.