Interaction between KDELR2 and HSP47 as a Key Determinant in Osteogenesis Imperfecta Caused by Bi-allelic Variants in KDELR2.

Osteogenesis imperfecta (OI) is characterized primarily by susceptibility to fractures with or without bone deformation. OI is genetically heterogeneous: over 20 genetic causes are recognized. We identified bi-allelic pathogenic KDELR2 variants as a cause of OI in four families. KDELR2 encodes KDEL endoplasmic reticulum protein retention receptor 2, which recycles ER-resident proteins with a KDEL-like peptide from the cis-Golgi to the ER through COPI retrograde transport. Analysis of patient primary fibroblasts showed intracellular decrease of HSP47 and FKBP65 along with reduced procollagen type I in culture media. Electron microscopy identified an abnormal quality of secreted collagen fibrils with increased amount of HSP47 bound to monomeric and multimeric collagen molecules. Mapping the identified KDELR2 variants onto the crystal structure of G. gallus KDELR2 indicated that these lead to an inactive receptor resulting in impaired KDELR2-mediated Golgi-ER transport. Therefore, in KDELR2-deficient individuals, OI most likely occurs because of the inability of HSP47 to bind KDELR2 and dissociate from collagen type I. Instead, HSP47 remains bound to collagen molecules extracellularly, disrupting fiber formation. This highlights the importance of intracellular recycling of ER-resident molecular chaperones for collagen type I and bone metabolism and a crucial role of HSP47 in the KDELR2-associated pathogenic mechanism leading to OI.

The Cockayne Syndrome Natural History (CoSyNH) study: clinical findings in 102 individuals and recommendations for care.

PURPOSE: Cockayne syndrome (CS) is a rare, autosomal-recessive disorder characterized by microcephaly, impaired postnatal growth, and premature pathological aging. It has historically been considered a DNA repair disorder; fibroblasts from classic patients often exhibit impaired transcription-coupled nucleotide excision repair. Previous studies have largely been restricted to case reports and small series, and no guidelines for care have been established. METHODS: One hundred two study participants were identified through a network of collaborating clinicians and the Amy and Friends CS support groups. Families with a diagnosis of CS could also self-recruit. Comprehensive clinical information for analysis was obtained directly from families and their clinicians. RESULTS AND CONCLUSION: We present the most complete evaluation of Cockayne syndrome to date, including detailed information on the prevalence and onset of clinical features, achievement of neurodevelopmental milestones, and patient management. We confirm that the most valuable prognostic factor in CS is the presence of early cataracts. Using this evidence, we have created simple guidelines for the care of individuals with CS. We aim to assist clinicians in the recognition, diagnosis, and management of this condition and to enable families to understand what problems they may encounter as CS progresses.Genet Med 18 5, 483-493.

Novel missense mutations in a conserved loop between ERCC6 (CSB) helicase motifs V and VI: Insights into Cockayne syndrome.

Cockayne syndrome is caused by biallelic ERCC8 (CSA) or ERCC6 (CSB) mutations and is characterized by growth restriction, microcephaly, developmental delay, and premature pathological aging. Typically affected patients also have dermal photosensitivity. Although Cockayne syndrome is considered a DNA repair disorder, patients with UV-sensitive syndrome, with ERCC8 (CSA) or ERCC6 (CSB) mutations have indistinguishable DNA repair defects, but none of the extradermal features of Cockayne syndrome. We report novel missense mutations affecting a conserved loop in the ERCC6 (CSB) protein, associated with the Cockayne syndrome phenotype. Indeed, the amino acid sequence of this loop is more highly conserved than the adjacent helicase motifs V and VI, suggesting that this is a crucial structural component of the SWI/SNF family of proteins, to which ERCC6 (CSB) belongs. These comprise two RecA-like domains, separated by an interdomain linker, which interact through helicase motif VI. As the observed mutations are likely to act through destabilizing the tertiary protein structure, this prompted us to re-evaluate ERCC6 (CSB) mutation data in relation to the structure of SWI/SNF proteins. Our analysis suggests that antimorphic mutations cause Cockayne syndrome and that biallelic interdomain linker deletions produce more severe phenotypes. Based on our observations, we propose that further investigation of the pathogenic mechanisms underlying Cockayne syndrome should focus on the effect of antimorphic rather than null ERCC6 (CSB) mutations.

Microdeletion 1p35.2: a recognizable facial phenotype with developmental delay.

We describe two patients with microdeletion 1p35.2, intrauterine growth retardation, small stature, hypermetropia, hearing impairment and developmental delay. Both patients have long, myopathic facies, with fine eyebrows, small mouths and micrognathia. We postulate a role for the histone deacetylase HDAC1 in the facial phenotype and suggest that deletion of KPNA6 may prevent transmission of the 1p35.2 deletion from affected girls to any offspring through impaired zygotic genome activation.

Juvenile idiopathic arthritis, mitral valve prolapse and a familial variant involving the integrin-binding fragment of FBN1.

Mutations in Fibrillin 1 (FBN1) are associated with Marfan syndrome and in some instances with the MASS phenotype (myopia, mitral valve prolapse, borderline non-progressive aortic root dilatation, skeletal features, and striae). Potential confusion over diagnosis and management in patients with borderline features has been addressed through the revised Ghent nosology, which emphasizes the importance of aortic root dilatation and ectopia lentis as features of Marfan syndrome. The overlapping and more common mitral valve prolapse syndrome is precluded by ectopia lentis or aortic dilatation. Among these clinically related conditions, there is no compelling evidence that genotype predicts phenotype, with the exception of neonatal Marfan syndrome, mutations in which cluster within FBN1 exons 24-32. Recent reports also link two very different phenotypes to changes in FBN1. Heterozygous mutations in transforming growth factor ß-binding protein-like domain 5 (TB5) can cause acromicric or geleophysic dysplasias-and mutations in the TB4 domain, which contains an integrin binding RGD loop, have been found in congenital scleroderma/stiff skin syndrome. We report on a variant in an evolutionarily conserved residue that stabilizes the integrin binding fragment of FBN1, associated with juvenile idiopathic arthritis, mitral valve prolapse or apparently normal phenotype in different family members.

ERCC1 mutations impede DNA damage repair and cause liver and kidney dysfunction in patients.

ERCC1-XPF is a multifunctional endonuclease involved in nucleotide excision repair (NER), interstrand cross-link (ICL) repair, and DNA double-strand break (DSB) repair. Only two patients with bi-allelic ERCC1 mutations have been reported, both of whom had features of Cockayne syndrome and died in infancy. Here, we describe two siblings with bi-allelic ERCC1 mutations in their teenage years. Genomic sequencing identified a deletion and a missense variant (R156W) within ERCC1 that disrupts a salt bridge below the XPA-binding pocket. Patient-derived fibroblasts and knock-in epithelial cells carrying the R156W substitution show dramatically reduced protein levels of ERCC1 and XPF. Moreover, mutant ERCC1 weakly interacts with NER and ICL repair proteins, resulting in diminished recruitment to DNA damage. Consequently, patient cells show strongly reduced NER activity and increased chromosome breakage induced by DNA cross-linkers, while DSB repair was relatively normal. We report a new case of ERCC1 deficiency that severely affects NER and considerably impacts ICL repair, which together result in a unique phenotype combining short stature, photosensitivity, and progressive liver and kidney dysfunction.

Functional characterisation of a novel ovarian cancer cell line, NUOC-1.

BACKGROUND: Cell lines provide a powerful model to study cancer and here we describe a new spontaneously immortalised epithelial ovarian cancer cell line (NUOC-1) derived from the ascites collected at a time of primary debulking surgery for a mixed endometrioid / clear cell / High Grade Serous (HGS) histology. RESULTS: This spontaneously immortalised cell line was found to maintain morphology and epithelial markers throughout long-term culture. NUOC-1 cells grow as an adherent monolayer with a doubling time of 58 hours. The cells are TP53 wildtype, positive for PTEN, HER2 and HER3 expression but negative for oestrogen, progesterone and androgen receptor expression. NUOC-1 cells are competent in homologous recombination and non-homologous end joining, but base excision repair defective. Karyotype analysis demonstrated a complex tetraploid karyotype. SNP array analysis of parent and derived subpopulations (NUOC-1-A1 and NUOC-1-A2) cells demonstrated heterogeneous cell populations with numerous copy number alterations and a pro-amplification phenotype. The characteristics of this new cell line lends it to be an excellent model for investigation of a number of the identified targets. MATERIALS AND METHODS: The cell line has been characterised for growth, drug sensitivity, expression of common ovarian markers and mutations, clonogenic potential and ability to form xenografts in SCID mice. Copy number changes and clonal evolution were assessed by SNP arrays.

Mutations in the histone methyltransferase gene KMT2B cause complex early-onset dystonia.

Histone lysine methylation, mediated by mixed-lineage leukemia (MLL) proteins, is now known to be critical in the regulation of gene expression, genomic stability, cell cycle and nuclear architecture. Despite MLL proteins being postulated as essential for normal development, little is known about the specific functions of the different MLL lysine methyltransferases. Here we report heterozygous variants in the gene KMT2B (also known as MLL4) in 27 unrelated individuals with a complex progressive childhood-onset dystonia, often associated with a typical facial appearance and characteristic brain magnetic resonance imaging findings. Over time, the majority of affected individuals developed prominent cervical, cranial and laryngeal dystonia. Marked clinical benefit, including the restoration of independent ambulation in some cases, was observed following deep brain stimulation (DBS). These findings highlight a clinically recognizable and potentially treatable form of genetic dystonia, demonstrating the crucial role of KMT2B in the physiological control of voluntary movement.

Glycosylation is an Androgen-Regulated Process Essential for Prostate Cancer Cell Viability.

Steroid androgen hormones play a key role in the progression and treatment of prostate cancer, with androgen deprivation therapy being the first-line treatment used to control cancer growth. Here we apply a novel search strategy to identify androgen-regulated cellular pathways that may be clinically important in prostate cancer. Using RNASeq data, we searched for genes that showed reciprocal changes in expression in response to acute androgen stimulation in culture, and androgen deprivation in patients with prostate cancer. Amongst 700 genes displaying reciprocal expression patterns we observed a significant enrichment in the cellular process glycosylation. Of 31 reciprocally-regulated glycosylation enzymes, a set of 8 (GALNT7, ST6GalNAc1, GCNT1, UAP1, PGM3, CSGALNACT1, ST6GAL1 and EDEM3) were significantly up-regulated in clinical prostate carcinoma. Androgen exposure stimulated synthesis of glycan structures downstream of this core set of regulated enzymes including sialyl-Tn (sTn), sialyl Lewis(X) (SLe(X)), O-GlcNAc and chondroitin sulphate, suggesting androgen regulation of the core set of enzymes controls key steps in glycan synthesis. Expression of each of these enzymes also contributed to prostate cancer cell viability. This study identifies glycosylation as a global target for androgen control, and suggests loss of specific glycosylation enzymes might contribute to tumour regression following androgen depletion therapy.

Metronidazole Toxicity in Cockayne Syndrome: A Case Series.

Cockayne syndrome (CS) is a rare genetic disorder characterized by small stature, intellectual disability, and accelerated pathologic aging. Through the Cockayne Syndrome Natural History Study, we have identified 8 cases of acute hepatic failure after metronidazole administration (8% of our cohort), 3 of which were fatal. The interval between initial administration and death was 6 to 11 days. Two of these patients also experienced acute neurologic deficit. Both hepatotoxicity and acute neurologic deficit have been reported previously as extremely rare adverse events after metronidazole administration. However, we have not identified any patients with CS who have received metronidazole without serious adverse effects. We recommend that a diagnosis of CS be considered an absolute contraindication to the use of metronidazole.

The androgen receptor controls expression of the cancer-associated sTn antigen and cell adhesion through induction of ST6GalNAc1 in prostate cancer.

Patterns of glycosylation are important in cancer, but the molecular mechanisms that drive changes are often poorly understood. The androgen receptor drives prostate cancer (PCa) development and progression to lethal metastatic castration-resistant disease. Here we used RNA-Seq coupled with bioinformatic analyses of androgen-receptor (AR) binding sites and clinical PCa expression array data to identify ST6GalNAc1 as a direct and rapidly activated target gene of the AR in PCa cells. ST6GalNAc1 encodes a sialytransferase that catalyses formation of the cancer-associated sialyl-Tn antigen (sTn), which we find is also induced by androgen exposure. Androgens induce expression of a novel splice variant of the ST6GalNAc1 protein in PCa cells. This splice variant encodes a shorter protein isoform that is still fully functional as a sialyltransferase and able to induce expression of the sTn-antigen. Surprisingly, given its high expression in tumours, stable expression of ST6GalNAc1 in PCa cells reduced formation of stable tumours in mice, reduced cell adhesion and induced a switch towards a more mesenchymal-like cell phenotype in vitro. ST6GalNAc1 has a dynamic expression pattern in clinical datasets, beingsignificantly up-regulated in primary prostate carcinoma but relatively down-regulated in established metastatic tissue. ST6GalNAc1 is frequently upregulated concurrently with another important glycosylation enzyme GCNT1 previously associated with prostate cancer progression and implicated in Sialyl Lewis X antigen synthesis. Together our data establishes an androgen-dependent mechanism for sTn antigen expression in PCa, and are consistent with a general role for the androgen receptor in driving important coordinate changes to the glycoproteome during PCa progression.

A case of mosaic trisomy 19q12-q13.2 with high BMI, macrocephaly, and speech delay: does USF2 determine size in the 19q phenotypes?

Hall et al. (2010) describe a boy with mosaic trisomy of the proximal part of 19q, with obesity, macrocephaly and global developmental delay. The patient is interesting with regard to his cytogenetic abnormality, which is smaller than those previously reported, and does not include the candidate obesity and insulin-resistance genes identified by other authors (Zung et al., 2007; Davidsson et al., 2010) as possible causes of the overweight/obesity seen in four of five previously documented patients. This suggests that a novel obesity locus may reside in the duplicated region 19q13.11­q13.2. We present a phenotypically similar boy with intrachromosomal insertion of material derived from proximal 19q into proximal 19p, causing mosaic trisomy 19q12­q13.2, and consider the role of USF2, a master transcriptional regulator of metabolic genes, in 19q phenotypes.