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Adipose tissue is a key regulator of whole-body metabolic fitness because of its role in controlling insulin sensitivity. Obesity is associated with hypertrophic adipocytes with impaired glucose absorption; a phenomenon existing in the ultra-rare monogenic disorder Alström syndrome consisting of severe insulin resistance. Inactivation of ALMS1 directly inhibits insulin-mediated glucose absorption in the white adipose tissue and induces severe insulin resistance, which leads to type 2 diabetes, accelerated non-alcoholic liver disease and fibrosis. These phenotypes were reversed by specific adipocyte-ALMS1 reactivation in vivo. Subsequently, ALMS1 was found to bind to PKC alpha in the adipocyte and upon insulin signaling PKC alpha is released from ALMS1. Alpha helices in the kinase domain of PKC alpha were therefore screened to identify a peptide sequence that interfered with the ALMS1-PKC alpha protein interaction. When incubated with cultured human adipocytes, the stapled peptide termed PATAS, for Peptide derived of PKC Alpha Targeting AlmS, triggered insulin-independent glucose absorption, de novo lipogenesis and cellular glucose utilization. In vivo, PATAS reduced whole-body insulin resistance, improved glucose intolerance, fasting glucose, liver steatosis and fibrosis in rodents. Thus, PATAS represents a novel first-in-class peptide that targets the adipocyte to ameliorate insulin resistance and its associated comorbidities.

Background Cockayne syndrome is a progressive multisystem genetic disorder linked to defective DNA repair and transcription. This rare condition encompasses a very wide spectrum of clinical severity levels ranging from severe prenatal onset to mild adult-onset subtypes. The rarity, complexity and variability of the disease make early diagnosis and severity assessment difficult. Based on similar approaches in other neurodegenerative disorders, we propose to validate diagnostic and severity scores for Cockayne syndrome. Methods Clinical, imaging and genetic data were retrospectively collected from 69 molecularly confirmed CS patients. A clinical diagnostic score and a clinical-radiological diagnostic score for CS were built using a multivariable logistic regression model with a stepwise variable selection procedure. A severity score for CS was designed on five items (head circumference, growth failure, neurosensorial signs, motor autonomy, communication skills) and validated by comparison with classical predefined severity subtypes of CS. Results Short stature, enophtalmos, hearing loss, cataracts, cutaneous photosensitivity, frequent dental caries, enamel hypoplasia, morphological abnormalities of the teeth, areflexia and spasticity were included in the clinical diagnostic score as being the most statistically relevant criteria. Appropriate weights and thresholds were assigned to obtain optimal sensitivity and specificity (95.7% and 86.4% respectively). The severity score was shown to be able to quantitatively differentiate classical predefined subtypes of CS and confirmed the continuous distribution of the clinical presentations in CS. Longitudinal follow-up of the severity score was able to reflect the natural course of the disease. Conclusion The diagnostic and severity scores for CS will facilitate early diagnosis and longitudinal evaluation of future therapeutic interventions. Prospective studies will be needed to confirm these findings.

Cerebro-oculo-facio-skeletal syndrome (COFS) is a rare autosomal recessive neurodegenerative disease belonging to the family of DNA repair disorders, characterized by microcephaly, congenital cataracts, facial dysmorphism and arthrogryposis. Here, we describe the detailed morphological and microscopic phenotype of three fetuses from two families harboring ERCC5/XPG likely pathogenic variants, and review the five previously reported fetal cases. In addition to the classical features of COFS, the fetuses display thymus hyperplasia, splenomegaly and increased hematopoiesis. Microencephaly is present in the three fetuses with delayed development of the gyri, but normal microscopic anatomy at the supratentorial level. Microscopic anomalies reminiscent of pontocerebellar hypoplasia are present at the infratentorial level. In conclusion, COFS syndrome should be considered in fetuses when intrauterine growth retardation is associated with microcephaly, arthrogryposis and ocular anomalies. Further studies are needed to better understand XPG functions during human development.

Cockayne syndrome (CS) is a rare disease caused by mutations in ERCC6/CSB or ERCC8/CSA. We report here the clinical, genetic, and functional analyses of three unrelated patients mutated in ERCC6/CSB with a severe phenotype. After clinical examination, two patients were investigated via next generation sequencing, targeting seventeen Nucleotide Excision Repair (NER) genes. All three patients harbored a novel, c.3156dup, homozygous mutation located in exon 18 of ERCC6/CSB that affects the C-terminal region of the protein. Sanger sequencing confirmed the mutation and the parental segregation in the three families, and Western blots showed a lack of the full-length protein. NER functional impairment was shown by reduced recovery of RNA synthesis with proficient unscheduled DNA synthesis after UV-C radiations in patient-derived fibroblasts. Despite sharing the same mutation, the clinical spectrum was heterogeneous among the three patients, and only two patients displayed clinical photosensitivity. This novel ERCC6 variant in Tunisian patients suggests a founder effect and has implications for setting-up prenatal diagnosis/genetic counselling in North Africa, where this disease is largely undiagnosed. This study reveals one of the rare cases of CS clinical heterogeneity despite the same mutation. Moreover, the occurrence of an identical homozygous mutation, which either results in clinical photosensitivity or does not, strongly suggests that this classic CS symptom relies on multiple factors.

Barded-Biedl syndrome (BBS) is a rare genetic disorder with an unmet medical need for retinal degeneration. Small-molecule drugs were previously identified to slow down the apoptosis of photoreceptors in BBS mouse models. Clinical translation was not practical due to the necessity of repetitive invasive intravitreal injections for pediatric populations. Non-invasive methods of retinal drug targeting are a prerequisite for acceptable adaptation to the targeted pediatric patient population. Here, we present the development and functional testing of a non-invasive, topical, magnetically assisted delivery system, harnessing the ability of magnetic nanoparticles (MNPs) to cargo two drugs (guanabenz and valproic acid) with anti-unfolded protein response (UPR) properties towards the retina. Using magnetic resonance imaging (MRI), we showed the MNPs’ presence in the retina of Bbs wild-type mice, and their photoreceptor localization was validated using transmission electron microscopy (TEM). Subsequent electroretinogram recordings (ERGs) demonstrated that we achieved beneficial biological effects with the magnetically assisted treatment translating the maintained light detection in Bbs−/− mice (KO). To our knowledge, this is the first demonstration of efficient magnetic drug targeting in the photoreceptors in vivo after topical administration. This non-invasive, needle-free technology expands the application of SMDs for the treatment of a vast spectrum of retinal degenerations and other ocular diseases.

Background: Cockayne syndrome is an autosomal recessive disorder caused by biallelic mutations in ERCC6 or ERCC8 genes. Aims: To study the clinical and mutation spectrum of Cockayne syndrome. Setting and Design: Medical Genetics Outpatient Department of Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow. This was a prospective study from 2007 to 2015. Materials and Methods: Clinical details were recorded, and sequencing of ERCC6 and ERCC8 were performed. Results and Conclusions: Of the six families, one family had a homozygous mutation in ERCC8 and the other five families had homozygous mutations in ERCC6. Novel variants in ERCC6 were identified in four families. Phenotypic features may vary from severe to mild, and a strong clinical suspicion is needed for diagnosis during infancy or early childhood. Hence, molecular diagnosis is needed for confirmation of diagnosis in a child with a suspicion of Cockayne syndrome. Prenatal diagnosis can be provided only if molecular diagnosis is established in the proband.

Obesity is a major risk factor for insulin resistance (IR) and its attendant complications. The pathogenic mechanisms linking them remain poorly understood, partly due to a lack of intermediary monogenic human phenotypes. Here, we report on a monogenic form of IR-prone obesity, Alström syndrome (ALMS). Twenty-three subjects with monogenic or polygenic obesity underwent hyperinsulinaemic-euglycemic clamping with concomitant adipose tissue (AT) microdialysis and an in-depth analysis of subcutaneous AT histology. We have shown a relative adipose tissue failure in monogenic obese cohort; a finding supported by observations in a novel conditional mouse model (Almsflin/flin) and ALMS1-silenced human primary adipocytes. Whereas, selective reactivation of ALMS1 gene in adipose tissue of an ALMS conditional knockdown mice model (Almsflin/flin;Adipo-Cre+/-) restores systemic insulin sensitivity and glucose tolerance. Hence, we show for the first time the relative adipose tissue failure in human obese cohorts to be a major determinant of accelerated IR without evidence of lipodystrophy. These new insights into adipocyte driven insulin resistance may assist development of adipose tissue targeted therapeutic strategies for diabetes.

Nucleotide excision repair associated diseases comprise overlapping phenotypes and a wide range of outcomes. The early stages still remain under-investigated and underdiagnosed, even although an early recognition of the first symptoms is of utmost importance for appropriate care and genetic counseling. We systematically collected clinical and molecular data from the literature and from newly diagnosed NER patients with neurological impairment, presenting clinical symptoms before the age of 12 months, including foetal cases. One hundred and eighty-five patients were included, 13 with specific symptoms during foetal life. Arthrogryposis, microcephaly, cataracts, and skin anomalies are the most frequently reported signs in early subtypes. Non ERCC6/CSB or ERCC8/CSA genes are overrepresented compared to later onset cohorts: 19% patients of this cohort presented variants in ERCC1, ERCC2/XPD, ERCC3/XPB or ERCC5/XPG. ERCC5/XPG is even the most frequently involved gene in foetal cases (10/13 cases, [4/7 families]). In this cohort, the mutated gene, the age of onset, the type of disease, severe global developmental delay, IUGR and skin anomalies were associated with earlier death. This large survey focuses on specific symptoms that should attract the attention of clinicians towards early-onset NER diagnosis in foetal and neonatal period, without waiting for the completeness of classical criteria.

Cockayne syndrome (CS) is a rare genetic disorder caused by mutations (dysfunction) in CSA and CSB. CS patients exhibit mild photosensitivity and severe neurological problems. Currently, CS diagnosis is based on the inefficiency of CS cells to recover RNA synthesis upon genotoxic (UV) stress. Indeed, upon genotoxic stress, ATF3, an immediate early gene is activated to repress up to 5000 genes encompassing its responsive element for a short period of time. On the contrary in CS cells, CSA and CSB dysfunction impairs the degradation of the chromatin-bound ATF3, leading to a permanent transcriptional arrest as observed by immunofluorescence and ChIP followed by RT-PCR. We analysed ChIP-seq of Pol II and ATF3 promoter occupation analysis and RNA sequencing-based gene expression profiling in CS cells, as well as performed immunofluorescence study of ATF3 protein stability and quantitative RT-PCR screening in 64 patient cell lines. We show that the analysis of few amount (as for example CDK5RAP2, NIPBL and NRG1) of ATF3 dependent genes, could serve as prominent molecular markers to discriminate between CS and non-CS patient’s cells. Such assay can significantly simplify the timing and the complexity of the CS diagnostic procedure in comparison to the currently available methods.

BackgroundCockayne syndrome (CS) is a rare, autosomal recessive multisystem disorder characterised by prenatal or postnatal growth failure, progressive neurological dysfunction, ocular and skeletal abnormalities and premature ageing. About half of the patients with symptoms diagnostic for CS show cutaneous photosensitivity and an abnormal cellular response to UV light due to mutations in either the ERCC8/CSA or ERCC6/CSB gene. Studies performed thus far have failed to delineate clear genotype-phenotype relationships. We have carried out a four-centre clinical, molecular and cellular analysis of 124 patients with CS.Methods and resultsWe assigned 39 patients to the ERCC8/CSA and 85 to the ERCC6/CSB genes. Most of the genetic variants were truncations. The missense variants were distributed non-randomly with concentrations in relatively short regions of the respective proteins. Our analyses revealed several hotspots and founder mutations in ERCC6/CSB. Although no unequivocal genotype-phenotype relationships could be made, patients were more likely to have severe clinical features if the mutation was downstream of the PiggyBac insertion in intron 5 of ERCC6/CSB than if it was upstream. Also a higher proportion of severely affected patients was found with mutations in ERCC6/CSB than in ERCC8/CSA.ConclusionBy identifying >70 novel homozygous or compound heterozygous genetic variants in 124 patients with CS with different disease severity and ethnic backgrounds, we considerably broaden the CSA and CSB mutation spectrum responsible for CS. Besides providing information relevant for diagnosis of and genetic counselling for this devastating disorder, this study improves the definition of the puzzling genotype-phenotype relationships in patients with CS.

Cockayne syndrome is an autosomal recessive multisystem disorder characterized by intellectual disability, microcephaly, severe growth failure, sensory impairment, peripheral neuropathy, and cutaneous sensitivity. This rare disease is linked to disease-causing variations in the ERCC6 (CSB) and ERCC8 (CSA) genes. Various degrees of severity have been described according to age at onset and survival, without any clear genotype-phenotype correlation. All types of nucleotide changes have been observed in CS genes, including splice variations mainly affecting the splice site consensus sequences. We report here the case of two brothers from a consanguineous family presenting a severe but long-term survival phenotype of Cockayne syndrome. We identified in the patients a homozygous deep intronic nucleotide variation causing the insertion of a cryptic exon in the ERCC8 (CSA) transcript, by modifying intronic regulatory elements important for exon definition. The pathogenesis of the nucleotide variant NG_009289.1(NM_000082.3):c.173+1119G>C was validated in vitro with a reporter minigene system. To our knowledge, these are the first Cockayne patients described with this kind of disease-causing variation, though molecular mechanism underlying early onset symptoms and unexpected slow raise of progression of the disease remain to be elucidated.

International audience; Cilia are highly conserved and ubiquitously expressed organelles. Ciliary defects of genetic origins lead to ci-liopathies, in which retinal degeneration (RD) is one cardinal clinical feature. In order to efficiently find and design new therapeutic strategies the underlying mechanism of retinal degeneration of three murine model was compared. The rodent models correspond to three emblematic ciliopathies, namely: Bardet-Biedl Syndrome (BBS), Alström Syndrome (ALMS) and CEP290-mediated Leber Congenital Amaurosis (LCA). Scotopic rodent electroretinography (ERG) was used to test the retinal function of mice, Transmitted Electron microscopy (T.E.M) was performed to assess retinal structural defects and real-time PCR for targeted genes was used to monitor the expression levels of the major apoptotic Caspase-related pathways in retinal extracts to identify pathological pathways driving the RD in order to identify potential therapeutic targets. We found that BBS and CEP290-mediated LCA mouse models exhibit perinatal retinal degeneration associated with rhodopsin mis-localization in the photoreceptor and the induction of an Endoplasmic Reticulum (ER) stress. On the other hand, the tested ALMS mouse model, displayed a slower degeneration phenotype, with no Rhodopsin mislocalization nor ER-stress activity. Our data points out that behind the general phenotype of vision loss associated with these ciliopathies, the mechanisms and kinetics of disease progression are different.

Cockayne syndrome (CS) is a multisystem degenerative disorder divided in 3 overlapping subtypes, with a continuous phenotypic spectrum: CS2 being the most severe form, CS1 the classical form and CS3 the late-onset form. Failure to thrive and growth difficulties are among the most consistent features of CS, leaving affected individuals vulnerable to numerous medical complications, including adverse effects of undernutrition, abrupt overhydration and overfeeding. There is thus a significant need for specific growth charts. We retrospectively collected growth parameters from genetically-confirmed CS1 and CS2 patients, used the GAMLSS package to construct specific CS growth charts compared to healthy children from WHO and CDC databases. Growth data were obtained from 88 CS patients with a total of 1626 individual growth data points. 49 patients were classified as CS1 and 39 as CS2 with confirmed mutations in CSB/ERCC6, CSA/ERCC8 or ERCC1 genes. Individuals with CS1 initially have normal growth parameters; microcephaly occurs from 2 months whereas onset of weight and height restrictions appear later, between 5 and 22 months. In CS2, growth parameters are already below standard references at birth or drop below the 5th percentile before 3 months. Microcephaly is the first parameter to show a delay, appearing around 2 months in CS1 and at birth in CS2. Height and head circumference are more severely affected in CS2 compared to CS1 whereas weight curves are similar in CS1 and CS2 patients. These new growth charts will serve as a practical tool to improve the nutritional management of children with CS.

Background Cockayne Syndrome (CS) is a rare autosomal recessive multi-systemic disorder, characterized; by developmental delay, microcephaly, severe growth failure and sensorial impairment. Renal complications have been reported but remain underinvestigated. The objective of this study was to perform a review of renal disease in a cohort of CS patients. Methods We retrospectively collected relevant clinical, biochemical and genetic data from a cohort of 136 genetically confirmed CS patients. Blood pressure (BP), proteinuria, albuminemia, uric acid, creatinine clearance, renal ultrasounds and renal biopsy result were analysed. Results Thirty-two patients had a renal investigation. We found that 69% of investigated patients had a renal disorder and/or an elevated BP. Fifteen out of 21 patients (71% of investigated patients) had an increased BP, 10 out of 16 patients (62% of investigated patients) presented with proteinuria and 4 of them had a nephrotic syndrome. Thirteen patients out of 29 (45%) had a decreased Glomerular Filtration Rate (GFR), 18 out of 25 patients (72%) had a hyperuricemia. No correlation with the genetic background or clinical types of CS was found, except for the renal clearance. Conclusions Renal disease, increased blood pressure and hyperuricemia were highly prevalent in our study. We believe that CS patients should benefit from a nephrological follow-up and that anti-uric acid drug and Angiotensin-converting enzyme (ACE) inhibitor should be discussed in these patients.

Ciliopathies are heterogeneous disorders sharing different clinical signs due to a defect at the level of the primary cilia/centrosome complex. Postaxial polydactyly is frequently reported in ciliopathies, especially in Bardet-Biedl syndrome (BBS). Clinical features and genetic results observed in a pair of dizygotic twins with BBS are reported. The following manifestations were present: retinitis pigmentosa, bilateral insertional polydactyly, cognitive impairment and renal dysfunction. X-rays of the hands confirmed the presence of a 4th mesoaxial extra-digit with Y-shaped metacarpal bones. The sequencing of LZTFL1 identified a missense mutation (NM_020347.2: p.Leu87Pro; c.260T>C) and a nonsense mutation (p.Glu260*; c.778G>T), establishing a compound heterozygous status for the twins. A major decrease of LZTFL1 transcript and protein was observed in the patient's fibroblasts. This is the second report of LZTFL1 mutations in BBS patients confirming LZTFL1 as a BBS gene. Interestingly, the only two families reported in literature thus far with LZTFL1 mutations have in common mesoaxial polydactyly, a very uncommon feature for BBS. This special subtype of polydactyly in BBS patients is easily identified on clinical examination and prompts for priority sequencing of LZTFL1 (BBS17).

Background Deficient nucleotide excision repair (NER) activity causes a variety of autosomal recessive diseases including xeroderma pigmentosum (XP) a disorder which pre-disposes to skin cancer, and the severe multisystem condition known as Cockayne syndrome (CS). In view of the clinical overlap between NER-related disorders, as well as the existence of multiple phenotypes and the numerous genes involved, we developed a new diagnostic approach based on the enrichment of 16 NER-related genes by multiplex amplification coupled with next-generation sequencing (NGS). Methods Our test cohort consisted of 11 DNA samples, all with known mutations and/or non pathogenic SNPs in two of the tested genes. We then used the same technique to analyse samples from a prospective cohort of 40 patients. Multiplex amplification and sequencing were performed using AmpliSeq protocol on the Ion Torrent PGM (Life Technologies). Results We identified causative mutations in 17 out of the 40 patients (43 %). Four patients showed biallelic mutations in the ERCC6(CSB) gene, five in the ERCC8(CSA) gene: most of them had classical CS features but some had very mild and incomplete phenotypes. A small cohort of 4 unrelated classic XP patients from the Basque country (Northern Spain) revealed a common splicing mutation in POLH (XP-variant), demonstrating a new founder effect in this population. Interestingly, our results also found ERCC2(XPD), ERCC3(XPB) or ERCC5(XPG) mutations in two cases of UV-sensitive syndrome and in two cases with mixed XP/CS phenotypes. Conclusions Our study confirms that NGS is an efficient technique for the analysis of NER-related disorders on a molecular level. It is particularly useful for phenotypes with combined features or unusually mild symptoms. Targeted NGS used in conjunction with DNA repair functional tests and precise clinical evaluation permits rapid and cost-effective diagnosis in patients with NER-defects. Electronic supplementary material The online version of this article (doi:10.1186/s13023-016-0408-0) contains supplementary material, which is available to authorized users.

Ciliopathies, a class of rare genetic disorders, present often with retinal degeneration caused by protein transport defects between the inner segment and the outer segment of the photoreceptors. Bardet-Biedl syndrome is one such ciliopathy, genetically heterogeneous with 17 BBS genes identified to date, presenting early onset retinitis pigmentosa. By investigating BBS12-deprived retinal explants and the Bbs12(-/-) murine model, we show that the impaired intraciliary transport results in protein retention in the endoplasmic reticulum. The protein overload activates a proapoptotic unfolded protein response leading to a specific Caspase12-mediated death of the photoreceptors. Having identified a therapeutic window in the early postnatal retinal development and through optimized pharmacological modulation of the unfolded protein response, combining three specific compounds, namely valproic acid, guanabenz, and a specific Caspase12 inhibitor, achieved efficient photoreceptor protection, thereby maintaining light detection ability in vivo.

Summary Studying ciliopathies, like the Bardet-Biedl syndrome (BBS), allow the identification of signaling pathways potentially involved in common diseases, sharing phenotypic features like obesity or type 2 diabetes. Given the close association between obesity and insulin resistance, obese BBS patients would be expected to be insulin resistant. Surprisingly, we found that a majority of obese BBS patients retained normal glucose tolerance and insulin sensitivity. Patient's adipose tissue biopsies revealed upregulation of adipogenic genes and decrease of inflammatory mediators. In vitro studies on human primary mesenchymal stem cells (MSCs) showed that BBS12 inactivation facilitated adipogenesis, increased insulin sensitivity, and glucose utilization. We generated a Bbs12 −/− mouse model to assess the impact of Bbs12 inactivation on adipocyte biology. Despite increased obesity, glucose tolerance was increased with specific enhanced insulin sensitivity in the fat. This correlated with an active recruitment of MSCs resulting in adipose tissue hyperplasia and decreased in inflammation.

We have identified TUBGCP4 variants in individuals with autosomal-recessive microcephaly and chorioretinopathy. Whole-exome sequencing performed on one family with two affected siblings and independently on another family with one affected child revealed compound-heterozygous mutations in TUBGCP4. Subsequent Sanger sequencing was performed on a panel of individuals from 12 French families affected by microcephaly and ophthalmic manifestations, and one other individual was identified with compound-heterozygous mutations in TUBGCP4. One synonymous variant was common to all three families and was shown to induce exon skipping; the other mutations were frameshift mutations and a deletion. TUBGCP4 encodes γ-tubulin complex protein 4, a component belonging to the γ-tubulin ring complex (γ-TuRC) and known to regulate the nucleation and organization of microtubules. Functional analysis of individual fibroblasts disclosed reduced levels of the γ-TuRC, altered nucleation and organization of microtubules, abnormal nuclear shape, and aneuploidy. Moreover, zebrafish treated with morpholinos against tubgcp4 were found to have reduced head volume and eye developmental anomalies with chorioretinal dysplasia. In summary, the identification of TUBGCP4 mutations in individuals with microcephaly and a spectrum of anomalies in eye development, particularly photoreceptor anomalies, provides evidence of an important role for the γ-TuRC in brain and eye development.

Background Bardet–Biedl Syndrome (BBS) is a genetically heterogeneous ciliopathy with clinical cardinal features including retinal degeneration, obesity and renal dysfunction. To date, 20 BBS genes have been identified with BBS10 being a major BBS gene found to be mutated in almost 20 percent of all BBS patients worldwide. It codes for the BBS10 protein which forms part of a chaperone complex localized at the basal body of the primary cilium. Renal dysfunction in BBS patients is one of the major causes of morbidity in human patients and is associated initially with urinary concentration defects related to water reabsorption impairment in renal epithelial cells. The aim of this study was to study and compare the impact of a total Bbs10 inactivation (Bbs10−/−) with that of a specific renal epithelial cells inactivation (Bbs10 fl/fl; Cdh16-Cre+/−). Results We generated the Bbs10−/−and Bbs10 fl/fl; Cadh16-Cre+/− mouse model and characterized them. Bbs10−/− mice developed obesity, retinal degeneration, structural defects in the glomeruli, polyuria associated with high circulating arginine vasopressin (AVP) concentrations, and vacuolated, yet ciliated, renal epithelial cells. On the other hand, the Bbs10 fl/fl; Cadh16-Cre+/−mice displayed no detectable impairment. Conclusions These data highlight the importance of a systemic Bbs10 inactivation to trigger averted renal dysfunction whereas a targeted absence of BBS10 in the renal epithelium is seemingly non-deleterious. Electronic supplementary material The online version of this article (doi:10.1186/s13630-015-0019-8) contains supplementary material, which is available to authorized users.

Objective Cockayne syndrome is an autosomal recessive leukodystrophy and multisystem disorder characterized by mental retardation, microcephaly, severe growth failure, sensorial impairment, peripheral neuropathy and cutaneous photosensitivity. It belongs to the family of DNA repair and transcription disorders together with xeroderma pigmentosum and trichothiodystrophy. Clinical and genetic diagnosis still remains challenging. Our goal was to develop a unique and efficient mutation-screening strategy for Cockayne syndrome and related disorders and to improve our understanding of the clinical spectrum of these conditions. Methods We have designed a novel targeted high-throughput sequencing approach for the diagnosis of Cockayne syndrome and related DNA repair disorders. We have studied 30 patients presenting with the cardinal clinical features of Cockayne syndrome or related DNA repair disorders. Results We have identified the causative mutations in 14 of the 30 patients. Three patients showed biallelic mutations in the ERCC6/CSB gene, 2 patients in the ERCC8/CSA gene, 1 patient in the ERCC2/XPD gene, 1 patient in the ERCC3/XPB, 1 patient in the ERCC5/XPG, 6 in the POLH gene. We present the clinical, neurological and radiological phenotypes of these patients with regard to our experience of a well-characterized cohort of more than 100 Cockayne patients previously studied in our center and we discuss the implications for diagnosis and prognosis purposes. Conclusion This novel approach enables us to rapidly confirm the genetic diagnosis of Cockayne syndrome and related disoders and to unravel the molecular defect in atypical and overlapping clinical presentations.

The autosomal recessive disorder, Bardet-Biedl syndrome (BBS) is an iconic ciliopathy, clinically characterized by obesity, retinopathy, polydactyly and renal dysfunction. To date, 19 BBS genes have been identified, with BBS10 being one of the most commonly mutated genes in human patients. The historical origin of the BBS-induced obesity has been associated with leptin resistance correlated with hyperleptinemia as well as decreased signaling in the appetite-governing arcuate nucleus neurons (ARC) of the hypothalamus. The ARC controls energy homeostasis, food intake and energy expenditure, through the detection of peripheral hormones by POMC and AgRP/NPY expressing neurons. POMC neurons are anorexigenic while NPY/AgRP are orexigenic, and both are ciliated cells. Several hormone receptors have ciliary localization, as the leptin receptor, and inactivation of the BBS proteins results in their mislocalization and signaling impairment. The present work aims at investigating the origins of obesity in the BBS by comparing the phenotype of a BBS10 total knockout (Bbs10-/-) with that of two BBS10 hypothalamic-specific KO mice: namely the POMC (Bbs10fl/fl;POMC-Cre+/-) and the AgRP (Bbs10fl/fl;AgRP-Cre+/-). Bbs10-/- mice develop obesity, together with other BBS cardinal traits, but surprisingly, both Bbs10fl/fl;AgRP-Cre+/- and Bbs10fl/fl;POMC-Cre+/- display a lean phenotype. Further characterizations of these mice highlighted the activation of compensatory mechanisms in response to the specific BBS10 inactivation probably forestalling the obese phenotype. These results indicate the complexity of the BBS-related obese phenotype, and support the need for an integrative approach that would include the contribution of other peripheral organs to better understand the origins of obesity in BBS.