Elucidation of the regulation of an adult cuticle gene Acp65A by the transcription factor Broad.

Broad (BR), an ecdysone-inducible transcription factor, is a major determinant of the pupal stage. The misexpression of BR-Z1 isoform (BR-Z1) during adult development of Drosophila melanogaster prevents the expression of the adult cuticle protein 65A gene (Acp65A). We found that the proximal 237 bp of the 5' flanking region of Acp65A were sufficient to mediate this suppression. A targeted point mutation of a putative BR-Z1 response element (BRE) within this region showed that it was not involved. Drosophila hormone receptor-like 38 (DHR38) is required for Acp65A expression. We found that BR-Z1 repressed DHR38 expression and that BR's inhibition of Acp65A expression was rescued by exogenous expression of DHR38. Thus, BR-Z1 suppresses Acp65A expression by preventing the normal up-regulation of DHR38 at the time of adult cuticle formation.

The cis-regulatory sequences required for expression of the Drosophila melanogaster adult cuticle gene ACP65A.

Post-embryonic development in insects requires successive molts. Molts are triggered by ecdysteroids, and the nature of the molt (larval, pupal or adult) is determined by juvenile hormones. The genes encoding cuticle proteins are targets of both classes of hormones, and therefore are interesting models to study hormone action at the molecular level. The Drosophila ACP65A cuticle gene is expressed exclusively during the synthesis of the adult exoskeleton, in epidermal domains synthesising flexible cuticle. We have examined the cis-regulatory sequences of ACP65A using phylogenetic comparisons and functional analysis, and find that only about 180 bp are essential, including an 81 bp intron. The restriction of ACP65A expression appears to depend on a strong repression mechanism.

The Drosophila ACP65A cuticle gene: deletion scanning analysis of cis-regulatory sequences and regulation by DHR38.

The regulatory sequences of the Drosophila ACP65A cuticle gene were analyzed in vivo in transgenic flies, using both fusion genes constructs and transposase-mediated deletions within a P element containing ACP65A regulatory sequences fused to the lacZ gene (deletion scanning). The sequences located between -594 and +161 are sufficient to confer both temporal and spatial expression specificities, indicating the presence of tissue-specific enhancers and response elements to hormone-induced factors. In addition, timing of expression and tissue-specificity appear to be controlled by distinct cis-regulatory elements, which suggests the existence of independent hormonal and tissue-specific signaling pathways. Gain and loss of function studies also implicate DHR38, the Drosophila homolog of the vertebrate NGFI-B-type nuclear receptors, as an important activator of the ACP65A gene.

[Chronic non-insulin deficient hyperglycemia in children]. / Hyperglycémie chronique non insulinoprive de l'enfant.

We report the clinical records of 45 children with abnormalities regarding glycemic regulation characterized by a non-insulin deficient hyperglycemia (NIDH), known under the different names of chemical diabetes, sub-clinical diabetes and more recently MODY. These 45 children belong to 31 families with 532 relatives comprising 137 cases of NIDH which could have been studied. The symptoms of this biochemical abnormality, the pathophysiology of which is not yet clearly understood, are the following: lack of clinical manifestations, except for a variable and intermittent glycosuria; constant abnormal glucose tolerance tests, above 97 percentiles of the reference value with some variations over time; normal immunoreactive insulin levels; percentage of glycosylated hemoglobin at the upper range of normal; dominant autosomal genetic transmission and no association with HLA markers like in insulin-dependent diabetes; lack of degenerative complications of the micro-angiopathic type, at least on these cases even after more than 30 years of follow-up; finally, no tendency towards insulin-dependent diabetes. The NIDH should not be confused with the slow and progressive beginning of insulin-dependent diabetes for which prolonged delay is needed to affirm the diagnosis. The frequency of the biochemical phenomena is about 1.8% of the cases of authentic diabetes mellitus occurring before the age of 15.