Submicroscopic chromosomal anomalies play an important role in the aetiology of intellectual disability (ID) and have been shown to account for up to 10% of non-syndromic forms. We present a family with two affected boys compatible with X-linked inheritance of a phenotype of severe neurodevelopmental disorder co-segregating with a deletion in Xp22.11 exclusively containing the PTCHD1 gene. Although the exact function of this gene is unknown to date, the structural overlap of its encoded patched domain-containing protein 1, the transmembrane protein involved in the sonic hedgehog pathway, and its expression in human cortex and cerebellum as well as in mice and drosophila brain suggests a causative role of its nullisomy in the developmental phenotype of our family. Our findings support the recent notions that PTCHD1 may play a role in X-linked intellectual disability (XLID) and autism disorders.

The determination of fetal point mutations from fetal cell-free DNA (cf-DNA) in maternal plasma is technically challenging due to the preponderance of maternal sequences. It has recently been shown that fetal cf-DNA sequences are smaller than maternal ones and that the selection of small cf-DNA fragments by size fractionation by agarose gel electrophoresis leads to the enrichment of fetal cf-DNA sequences, thereby permitting the detection of otherwise masked fetal point mutations. In a separate development, the use of MALDI-TOF MS has also been shown to facilitate the detection of fetal point mutations from cf-DNA in maternal plasma. In this study, a combination of these approaches was examined. cf-DNA was extracted from 18 maternal plasma samples, 10 taken at term and 8 obtained early in the second trimester. A total of 41 SNP loci were examined in size-fractionated and total cf-DNA using either a conventional homogeneous MassEXTEND (hME) assay or a nucleotide-specific single allele base extension reaction (SABER) assay. The analysis of total cf-DNA indicated that size fractionation considerably enhanced the sensitivity of the standard hME assay, especially for samples taken early in pregnancy. Size fractionation also rendered the signals obtained by the SABER assay more precise.

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Interstitial deletions of 1q4 are rare and present with different deletion breakpoints and variable phenotype. We report on the clinical and molecular cytogenetic findings in a girl with minor anomalies, midline defects including prenatally ascertained agenesis of the corpus callosum, epilepsy and developmental delay. A de novo 5.45 Mb deletion almost exclusively located within 1q42 was found to cause this phenotype, which shows significant overlap with the microdeletion 1q41q42 syndrome reported in a few patients except for the agenesis of the corpus callosum. However, deletions in patients with the 1q41q42 syndrome mainly extend into the 1q41 region with a region of overlap including the DISP1 gene involved in the SHH pathway, which is not part of the 1q42 deletion in our patient. We suggest that an interaction of genes involved in pathways of embryonic development rather than haploinsufficiency of single genes in the so-called critical regions is causing complex malformation syndromes due to cytogenetic microaberrations in the 1q4 region.

Juvenile polyposis syndrome (JPS) is a rare autosomal dominant disorder predisposing to gastrointestinal hamartomatous polyps and cancer with a pathogenic SMAD4 or BMPR1A germline mutation (1st-hit) being identified in about 40-50% of patients. Little is known, however, about the occurrence and nature of somatic alterations (2nd-hit) in SMAD4-/BMPR1A-related juvenile polyps. In this study, we screened 25 polyps from three patients carrying either a pathogenic SMAD4 (c.1244-1247delACAG) or BMPR1A (c.583C>T; p.Gln195*) germline mutation for somatic alterations. The SMAD4-related polyps were also analyzed for SMAD4 protein expression by immunohistochemistry. Despite comprehensive screening for loss of heterozygosity (LOH), mutations in the coding sequence, chromosomal rearrangements, and promoter methylation, no somatic alterations could be identified in 14 SMAD4-related polyps. SMAD4 protein expression, however, was lost in 8 (57%) of 14 juvenile polyps with 6 showing concomitant loss in both, the epithelial and stromal, compartments. In the BMPR1A-related polyps, five out of nine (56%) displayed LOH. Further analysis of selected polyps revealed that LOH was gene copy number neutral and had occurred in the epithelial compartment. The heterogeneity of genetic mutations and protein expression levels indicates that different modes of gene inactivation can be operational in SMAD4- and BMPR1A-related polyp formation. Our observation, that about half of BMPR1A-related polyps displayed LOH, predominantly in the epithelial compartment, is compatible with BMPR1A acting as a tumour suppressor gene. Still, it remains to be determined whether juvenile polyp development generally requires loss of BMPR1A expression or, as observed in some SMAD4-related polyps, can occur despite normal protein expression.

Although interpretation of aCGH results may be straightforward in the majority of cases, placental mosaicism may cause misinterpretations of rapid aCGH results on direct chorionic villi due to discrepant chromosomal constitutions of cytotrophoblast and mesenchymal villus core. Further investigations including cultures, fluorescence in situ hybridization and possible amniocentesis will still be required for interpretation of results.

Hutchinson-Gilford progeria syndrome (HGPS) is a genetic disorder displaying features reminiscent of premature senescence caused by germline mutations in the LMNA gene encoding lamin A and C, essential components of the nuclear lamina. By studying a family with homozygous LMNA mutation (K542N), we showed that HGPS can also be caused by mutations affecting both isoforms, lamin A and C. Here, we aimed to elucidate the molecular mechanisms underlying the pathogenesis in both, lamin A- (sporadic) and lamin A and C-related (hereditary) HGPS. For this, we performed detailed molecular studies on primary fibroblasts of hetero- and homozygous LMNA K542N mutation carriers, accompanied with clinical examinations related to the molecular findings. By assessing global gene expression we found substantial overlap in altered transcription profiles (13.7%; 90/657) in sporadic and hereditary HGPS, with 83.3% (75/90) concordant and 16.7% (15/90) discordant transcriptional changes. Among the concordant ones we observed down-regulation of TWIST2, whose inactivation in mice and humans leads to loss of subcutaneous fat and dermal appendages, and loss of expression in dermal fibroblasts and periadnexial cells from a LMNA K542N/K542N patient further confirming its pivotal role in skin development. Among the discordant transcriptional profiles we identified two key mediators of vascular calcification and bone metabolism, ENPP1 and OPG, which offer a molecular explanation for the major phenotypic differences in vascular and bone disease in sporadic and hereditary HGPS. Finally, this study correlates reduced TWIST2 and OPG expression with increased osteocalcin levels, thereby linking altered bone remodeling to energy homeostasis in hereditary HGPS.

The ultrastructure and morphogenesis of the micropylar apparatus (MPA) have been studied in follicles of the fungus gnatBradysia tritici. The MPA is formed by a group of follicle cells located at the anterior pole of the single large nurse cell. In principle, the MPA consists of two thickened plates made of vitelline membrane material, the lower (LMP) and upper micropylar plate (UMP). The former is synthesized by 3 follicle cells, the latter by 4 different follicle cells. The micropylar channel system consists of a central channel with a single outer orifice and three branches which reach the plasma membrane of the oocyte. The branches are moulded by cellular extensions of the LMP-forming cells which are sandwiched between the two growing micropylar plates. Microtubuli and microfilaments were identified parallel to the long axis of the cellular extensions. At the time of MPA synthesis the nurse cell is still large and hence the MPA-forming cells have no contact to the oocyte. At the end of oogenesis when the regression of the nurse cell is completed, the MPA becomes connected to the other parts of the egg shell. At this time an ultrastructurally homogeneous region forms in the adjacent ooplasm ("cytoplasmic cone"). The possible relevance of these cytological observations for the control of development is discussed.