Autosomal recessive cutis laxa (ARCL) describes a group of syndromal disorders that are often associated with a progeroid appearance, lax and wrinkled skin, osteopenia and mental retardation. Homozygosity mapping in several kindreds with ARCL identified a candidate region on chromosome 17q25. By high-throughput sequencing of the entire candidate region, we detected disease-causing mutations in the gene PYCR1. We found that the gene product, an enzyme involved in proline metabolism, localizes to mitochondria. Altered mitochondrial morphology, membrane potential and increased apoptosis rate upon oxidative stress were evident in fibroblasts from affected individuals. Knockdown of the orthologous genes in Xenopus and zebrafish led to epidermal hypoplasia and blistering that was accompanied by a massive increase of apoptosis. Our findings link mutations in PYCR1 to altered mitochondrial function and progeroid changes in connective tissues.

The regulated proliferation and differentiation of neural stem cells before the generation and migration of neurons in the cerebral cortex are central aspects of mammalian development. Periventricular neuronal heterotopia, a specific form of mislocalization of cortical neurons, can arise from neuronal progenitors that fail to negotiate aspects of these developmental processes. Here we show that mutations in genes encoding the receptor-ligand cadherin pair DCHS1 and FAT4 lead to a recessive syndrome in humans that includes periventricular neuronal heterotopia. Reducing the expression of Dchs1 or Fat4 within mouse embryonic neuroepithelium increased progenitor cell numbers and reduced their differentiation into neurons, resulting in the heterotopic accumulation of cells below the neuronal layers in the neocortex, reminiscent of the human phenotype. These effects were countered by concurrent knockdown of Yap, a transcriptional effector of the Hippo signaling pathway. These findings implicate Dchs1 and Fat4 upstream of Yap as key regulators of mammalian neurogenesis.

We used an exome-sequencing strategy and identified an allelic series of NOTCH2 mutations in Hajdu-Cheney syndrome, an autosomal dominant multisystem disorder characterized by severe and progressive bone loss. The Hajdu-Cheney syndrome mutations are predicted to lead to the premature truncation of NOTCH2 with either disruption or loss of the C-terminal proline-glutamate-serine-threonine-rich proteolytic recognition sequence, the absence of which has previously been shown to increase Notch signaling.

Excess exogenous retinoic acid (RA) has been well documented to have teratogenic effects in the limb and craniofacial skeleton. Malformations that have been observed in this context include craniosynostosis, a common developmental defect of the skull that occurs in 1 in 2500 individuals and results from premature fusion of the cranial sutures. Despite these observations, a physiological role for RA during suture formation has not been demonstrated. Here, we present evidence that genetically based alterations in RA signaling interfere with human development. We have identified human null and hypomorphic mutations in the gene encoding the RA-degrading enzyme CYP26B1 that lead to skeletal and craniofacial anomalies, including fusions of long bones, calvarial bone hypoplasia, and craniosynostosis. Analyses of murine embryos exposed to a chemical inhibitor of Cyp26 enzymes and zebrafish lines with mutations in cyp26b1 suggest that the endochondral bone fusions are due to unrestricted chondrogenesis at the presumptive sites of joint formation within cartilaginous templates, whereas craniosynostosis is induced by a defect in osteoblastic differentiation. Ultrastructural analysis, in situ expression studies, and in vitro quantitative RT-PCR experiments of cellular markers of osseous differentiation indicate that the most likely cause for these phenomena is aberrant osteoblast-osteocyte transitioning. This work reveals a physiological role for RA in partitioning skeletal elements and in the maintenance of cranial suture patency.

Hematoporphyrin derivative has been evaluated as a means of detecting malignancy in 121 patients suspected of having cancer. Areas examined included the cervix, vagina, tracheobronchial tree, esophagus, peritoneum and rectum. Dysplastic and neoplastic tissue was identified by red fluorescence whereas nonneoplastic tissue appeared grayish white to black. Thirty‐three of 35 primary malignancies of the cervix and vagina were detected by fluorescence. The technique was especially helpful for the identification of recurrent lesions. In the fluorescent endoscopy group, the region of malignancy was identified by fluorescence in 32 of the 34 cases in which the lesion was located where the activating light could reach it in sufficient intensity. Hematoporphyrin derivative is a valuable adjunct to detection and management of malignancy, especially in the patient who presents a problem of the extent, location or possible recurrence of a malignant lesion.

No abstract

Serpentine fibula polycystic kidney syndrome (SFPKS; MIM600330) is a rare skeletal dysplasia that has polycystic kidneys and dysmorphic facies as additional defining phenotypic components. The nosological classification of this disease has been debated as the condition shares features common to other skeletal dysplasias such as Melnick Needles syndrome (MNS; MIM309350) and Hajdu-Cheney Syndrome (HCS; MIM102500). Here, two previously reported cases of SFPKS are presented with emphasis on their phenotypic evolution. With the recent discovery that HCS is caused by mutations in NOTCH2, DNA from the both cases was examined and both were found to have truncating mutations in exon 34 of NOTCH2. The phenotypic evolution of SFPKS and this molecular analysis strongly suggest that SFPKS is part of the phenotypic spectrum of HCS and should no longer be classified as a distinct disease entity.

No abstract