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Although 22q11.2 deletion syndrome (22q11.2DS) is the most recurrent human microdeletion syndrome associated with a highly variable phenotype, little is known about the condition's true incidence and the phenotype at diagnosis. We performed a multicenter, retrospective analysis of postnatally diagnosed patients recruited by members of the Association des Cytogénéticiens de Langue Française (the French-Speaking Cytogeneticists Association). Clinical and cytogenetic data on 749 cases diagnosed between 1995 and 2013 were collected by 31 French cytogenetics laboratories. The most frequent reasons for referral of postnatally diagnosed cases were a congenital heart defect (CHD, 48.6%), facial dysmorphism (49.7%) and developmental delay (40.7%). Since 2007 (the year in which array comparative genomic hybridization (aCGH) was introduced for the routine screening of patients with intellectual disability), almost all cases have been diagnosed using FISH (96.1%). Only 15 cases (all with an atypical phenotype) were diagnosed with aCGH; the deletion size ranged from 745 to 2904 kb. The deletion was inherited in 15.0% of cases and was of maternal origin in 85.5% of the latter. This is the largest yet documented cohort of patients with 22q11.2DS (the most commonly diagnosed microdeletion) from the same population. French cytogenetics laboratories diagnosed at least 108 affected patients (including fetuses) per year from among a national population of ∼66 million. As observed for prenatal diagnoses, CHDs were the most frequently detected malformation in postnatal diagnoses. The most common CHD in postnatal diagnoses was an isolated septal defect.

Objectives: The aim of this study was to evaluate the relative risk of identifying fetal chromosomal anomalies after finding ultrasonographic (US) abnormalities in a high-risk population who underwent amniocentesis. Methods: A retrospective review of a cohort of patients with single pregnancies who underwent genetic amniocentesis was undertaken. Univariate and multivariate analysis were used to determine the best correlations between US findings and chromosomal abnormalities. Results: Overall, 191 chromosomal abnormalities were found in 5,604 fetuses (3.4%). Multivariate analysis showed chromosomal abnormalities were significant ly associated with anomalies of the central nervous system (OR = 4.4, 95% CI 2.2-8.7), face and neck (OR = 15.7, 95% CI 9.2-26.8), heart (OR = 5.4, 95% CI 2.6-11.2), abdomen (OR = 5.6, 95% CI 2.9-10.9), extremities (OR = 5.7, 95% CI 2.4-13.4), an increased nuchal fold (OR = 5.2, 95% CI 3.3-8.1), an intrauterine growth restriction (OR = 3.6, 95% CI 1.6-7.9) and a short femur (OR = 4.1, 95% CI 1.4-12.1). Conclusions: Our results confirm the validity of specific US markers in detecting chromosomal abnormalities in the fetus.

Background Klinefelter syndrome (KS), a common sex chromosome aneuploidy (47,XXY) is diagnosed prenatally with an incidence of 0.15%. The diagnosis is generally incidental, since there are no typical malformations on ultrasound (US). Once detected, genetic counseling is often difficult and the parents' decision to continue or terminate the pregnancy is greatly dependent on the amount and nature of the information provided. We sought to assess the pregnancy outcomes (i.e. continuation versus termination) and the influence of multidisciplinary centers for prenatal diagnosis on parental decisions in cases of KS. Methods From 1985 to 2009, 188 prenatal diagnoses of KS were made by 11 participating laboratories in mainland France. In each case, the karyotype indication, parental ages, year of prenatal testing, sampling procedure, karyotype, associated US findings and outcome were recorded. Results and conclusions The pregnancy termination rate declined markedly over time, from 46.9% before 1997 to 11.6% thereafter, in line with the introduction of new legislation on prenatal diagnosis for medical reasons and, more specifically, the creation of multidisciplinary prenatal diagnosis centers. However, an additional microdeletion in one KS infant who exhibited echogenic bowel on US was unfortunately diagnosed postnatally. This raises the question as to whether array comparative genomic hybridization should be prenatally advised when US abnormalities are detected, in line with advice for fetuses with a normal karyotype.

Intrachromosomal insertions are uncommon rearrangements, in which a chromosomal segment is intercalated into another part of the same chromosome. The insertion may occur in the same arm (paracentric) or in the other arm (pericentric). The cytogenetic recognition of these structurally rearranged chromosomes can be difficult, and intrachromosomal insertions can be easily mistaken for inversions. We describe a case of a familial pericentric insertion of chromosome 20, initially misdiagnosed as a pericentric inversion in the healthy carrier and then reinterpreted as insertion in an abnormal child with a recombinant chromosome. Fluorescence in situ hybridization (FISH) allowed us to confirm the mechanism of recombinant formation and to locate the three breakpoints precisely. Our cytogenetically unbalanced epileptic patient carried a 20q deletion and 20p duplication, and the genes, CHRNA4 and KCNQ2 that have been implicated in autosomal dominant epilepsy, were deleted. The haplo-insufficiency of these two genes may contribute to the cause of epilepsy in patients with ring chromosome 20.

A locus on distal 9p has been reported to be deleted in patients with mental retardation, craniofacial dysmorphic traits, notably trigonocephaly, and a high frequency of genital and/or gonadal anomalies (Alfi's syndrome).1 More recently, some cases of 46,XY male to female sex reversal without dysmorphic traits have been described in association with distal deletions of 9p.2–5 46,XY patients described so far have had gonadal anomalies ranging from streak gonads, to partially masculinised dysgenetic gonads, to normal testes. A family of genes containing a unique zinc finger DNA binding domain, which has been called DM, as it is contained in two proteins involved in invertebrate sex determination, doublesex and mab-3, has recently been recognised. Three genes belonging to this family have been identified on 9p24.3, immediately proximal to the centromeric boundary of the minimal region, which is required in two copies for testis development.5 The first gene identified was termed DMRT1 and the two additional DM gene family members are placed in tandem more distally to the breakpoint of the minimal deleted region.6,7 DMRT1 is transcribed only in the embryonic gonads of both sexes and in fetal and adult testis, and is required for postnatal differentiation of both somatic and germ cells in the mouse testis.8 Therefore, this gene is a good candidate to explain the 46,XY sex reversal associated with 9p deletions. Recently, a 1 year old 46,XX female patient with premature ovarian failure and deletion of 9p was reported.9 This led to the suggestion of a role for a gene located on 9p in both male and female gonadal development. DMRT1 represents a good candidate for a function in both sexes as it is expressed in the genital ridge in both sexes in mouse and humans.7,8 Here, we report …

Objet Dans le noyau interphasique, la chromatine est organisee en territoires chromosomiques (TC) [1] . Le lien entre cette organisation et la regulation de l’expression du genome reste meconnu. Afin de preciser cette organisation, nous avons etudie un modele de desorganisation : les aneuploidies en supposant que la presence d’un chromosome surnumeraire pouvait entrainer une perturbation de la distribution des TC, elle-meme conduisant a une modification de l’activite transcriptionnelle. Methodes Etude de la position des TC 18 et 21 par FISH 3D dans les noyaux interphasiques de fœtus aneuploides et temoins. Comparaison des volumes des noyaux et des TC. Parallelement, une analyse transcriptomique comparative pangenomique des cellules a ete realisee afin d’objectiver des deregulations d’expression. Resultats Nous n’avons pas observe de difference de positions des TC 18 et 21 entre les fœtus atteints et les temoins. Si les volumes nucleaires n’etaient pas modifies, ceux des TC l’etaient. Nous avons mis en evidence des modifications d’expression d’une partie des genes portes par les chromosomes d’interet ; mais egalement de genes sur les autres chromosomes. Discussion En cas d’aneuploidie, l’organisation des TC aneuploides dans le noyau semble globalement respectee. Il existerait cependant une diminution du volume de ces TC sans modification du volume des noyaux, interrogeant au detriment de quel compartiment, se fait cette compaction. L’analyse transcriptomique renforce l’idee d’une combinaison d’un effet de dosage genique et d’une rupture de l’homeostasie : aux genes deregules portes par les chromosomes trisomiques, s’ajoutent des modifications d’expression du reste du genome. Ces deregulations concernent de multiples voies impliquees dans le developpement mais aussi des genes au potentiel role dans l’apparition de traits phenotypiques. Conclusion Il semblerait exister un lien entre le desequilibre genique des chromosomes aneuploides et les deregulations de l’ensemble du genome. La participation de la reorganisation des TC reste a affiner.

Hirschsprung disease (HSCR) is a common malformation of neural-crest–derived enteric neurons that is frequently associated with other congenital abnormalities. The SMADIP1 gene recently has been recognized as disease causing in some patients with 2q22 chromosomal rearrangement, resulting in syndromic HSCR with mental retardation, with microcephaly, and with facial dysmorphism. We screened 19 patients with HSCR and mental retardation and eventually identified large-scale SMADIP1 deletions or truncating mutations in 8 of 19 patients. These results allow further delineation of the spectrum of malformations ascribed to SMADIP1 haploinsufficiency, which includes frequent features such as hypospadias and agenesis of the corpus callosum. Thus, SMADIP1, which encodes a transcriptional corepressor of Smad target genes, may play a role not only in the patterning of neural-crest–derived cells and of CNS but also in the development of midline structures in humans.

Fourteen lysosomal enzymes were compared in 20 cultured cell lines from chorionic biopsy and corresponding embryonic tissue after voluntary abortions. Enzymatic expression appears to be similar in cultured cells from both sources with some slightly higher levels for chorionic villi. We stress the importance of culturing chorionic villi especially in the case of enzymes (alpha-L-iduronidase) or diseases (I cell disease) whose expression is unusual in fresh trophoblast tissue.