New criteria for improved diagnosis of Bardet-Biedl syndrome: results of a population survey

Clinical Characteristics and Genetic Variants of a Large Cohort of Patients with Retinitis Pigmentosa Using Multimodal Imaging and Next Generation Sequencing

This retrospective study identifies patients with RP at the Inherited Retinal Disease Clinic at the University of Minnesota (UMN)/M Health System who had genetic testing via next generation sequencing. A database was curated to record history and examination, genetic findings, and ocular imaging. Causative pathogenic and likely pathogenic variants were recorded. Disease status was further characterized by ocular coherence tomography (OCT) and fundus autofluorescence (AF). Our study cohort included a total of 199 patients evaluated between 1 May 2015-5 August 2022. The cohort included 151 patients with non-syndromic RP and 48 with syndromic RP. Presenting symptoms included nyctalopia (85.4%) photosensitivity/hemeralopia (60.5%), and decreased color vision (55.8%). On average, 38.9% had visual acuity of worse than 20/80. Ellipsoid zone band width on OCT scan of less than 1500 μm was noted in 73.6%. Ninety-nine percent had fundus autofluorescence (AF) findings of a hypo- or hyper-fluorescent ring within the macula and/or peripheral hypo-AF. Of the 127 subjects who underwent genetic testing, a diagnostic pathogenic and/or likely pathogenic variant was identified in 67 (52.8%) patients-33.3% of syndromic RP and 66.6% of non-syndromic RP patients had a diagnostic gene variant identified. It was found that 23.6% of the cohort had negative genetic testing results or only variants of uncertain significance identified, which were deemed as non-diagnostic. We concluded that patients with RP often present with advanced disease. In our population, next generation sequencing panels identified a genotype consistent with the exam in just over half the patients. Additional work will be needed to identify the underlying genetic etiology for the remainder.

Modelling renal defects in Bardet-Biedl syndrome patients using human iPS cells

Bardet-Biedl syndrome (BBS) is a ciliopathy with pleiotropic effects on multiple tissues, including the kidney. Here we have compared renal differentiation of iPS cells from healthy and BBS donors. High content image analysis of WT1-expressing kidney progenitors showed that cell proliferation, differentiation and cell shape were similar in healthy, BBS1, BBS2, and BBS10 mutant lines. We then examined three patient lines with BBS10 mutations in a 3D kidney organoid system. The line with the most deleterious mutation, with low BBS10 expression, expressed kidney marker genes but failed to generate 3D organoids. The other two patient lines expressed near normal levels of BBS10 mRNA and generated multiple kidney lineages within organoids when examined at day 20 of organoid differentiation. However, on prolonged culture (day 27) the proximal tubule compartment degenerated. Introducing wild type BBS10 into the most severely affected patient line restored organoid formation, whereas CRISPR-mediated generation of a truncating BBS10 mutation in a healthy line resulted in failure to generate organoids. Our findings provide a basis for further mechanistic studies of the role of BBS10 in the kidney.

Laparoscopic Sleeve Gastrectomy in a Morbidly Obese Pediatric Patient With Bardet-Biedl Syndrome

Data on the effect of bariatric surgery for syndromic obesity are lacking. This case report presents the preoperative evaluation and perioperative outcomes of a 7-year-old pediatric patient with Bardet-Biedl syndrome (BBS) who underwent sleeve gastrectomy. The male patient was referred to our department for the surgical treatment of his obesity. His preoperative body mass index (BMI) was 55.2 kg/m² (weight, 83.5 kg), and he was above the 99^th percentile for age and gender. The patient underwent laparoscopic sleeve gastrectomy. The postoperative period was uneventful. Six months after the operation, the patient's weight decreased to 50 kg (BMI, 28.72 kg/m²). Weight loss was maintained until 3 years after surgery. Dyslipidemia and nonalcoholic fatty liver disease were significantly alleviated. Laparoscopic sleeve gastrectomy may be a safe and effective treatment for morbid BBS-related obesity in pediatric patients. Further data are needed to confirm the long-term efficacy and safety of bariatric surgery in BBS.

Interview-Based Patient- and Caregiver-Reported Experiences of Hunger and Improved Quality of Life with Setmelanotide Treatment in Bardet-Biedl Syndrome

INTRODUCTION

Bardet-Biedl syndrome (BBS) is a rare genetic disease associated with hyperphagia, a pathologic insatiable hunger, due to impaired signaling in the melanocortin-4 receptor (MC4R) pathway. The impact of hyperphagia on the lives of patients with BBS and their families has not been fully characterized.

METHODS

Patients with BBS or their caregivers who participated in clinical trials of the MC4R agonist setmelanotide (NCT03013543 and NCT03746522) were included in this qualitative study. Telephone interviews were conducted using a semistructured interview guide to explore patient experience and caregiver observations of hyperphagia before and during setmelanotide treatment.

RESULTS

Nineteen interviews (8 patients, 11 caregivers) were conducted. The term "hunger" (rather than "hyperphagia") was used in interviews to ensure common terminology. Before setmelanotide treatment, all participants described their (or their child's) hunger as all-consuming, leading to an obsessive focus on food. Nine participants recalled intense, continuous hunger, and most participants (5 patients, 10 caregivers) reported lack of control with eating. Negative impacts on patients' lives included difficulties with concentration, emotional and physical manifestations, and impaired relationships. All participants experienced or observed improvements in hunger and health outcomes during treatment, the most meaningful of which included weight loss and decrease in obsessive focus on food and food-seeking behaviors. All participants reported improvements in either physical and/or emotional well-being and being satisfied with setmelanotide.

CONCLUSIONS

Hyperphagia and resulting food-seeking behaviors have notable negative impacts on quality of life in patients with BBS and caregivers. Setmelanotide improved hyperphagia, reduced body weight and obsessive focus on food, and facilitated improvements in physical and emotional well-being for both patients and caregivers.

TRIAL REGISTRATION

NCT03013543 and NCT03746522.

McKusick-Kaufman Syndrome: A Case Report With an Emphasis on Perinatal Diagnosis and Genetic Counseling

McKusick-Kaufman syndrome is a rare genetic disorder that affects limb development, genital formation, and heart function. It is caused by mutations in the MKKS gene on chromosome 20. Individuals with this condition may have extra fingers or toes, fused labia or undescended testes, and, less commonly, severe heart defects. Diagnosis involves a physical examination and genetic testing, while treatment focuses on symptom management, including surgical intervention if necessary. The prognosis varies depending on the severity of associated complications. In a recent case, a 27-year-old woman with fetal hydrometrocolpos gave birth to a female neonate with extra digits on both hands and feet, fused labia, and a small vaginal opening. The neonate also had a large abdominal cystic mass, and echocardiography revealed a patent foramen ovale. Genetic testing confirmed an MKKS gene mutation, and the hydrometrocolpos required surgical management. Early diagnosis and intervention can improve outcomes for individuals with this syndrome.

Renal ciliopathies: promising drug targets and prospects for clinical trials

INTRODUCTION

Renal ciliopathies represent a collection of genetic disorders characterized by deficiencies in the biogenesis, maintenance, or functioning of the ciliary complex. These disorders, which encompass autosomal dominant polycystic kidney disease (ADPKD), autosomal recessive polycystic kidney disease (ARPKD), and nephronophthisis (NPHP), typically result in cystic kidney disease, renal fibrosis, and a gradual deterioration of kidney function, culminating in kidney failure.

AREAS COVERED

Here we review the advances in basic science and clinical research into renal ciliopathies which have yielded promising small compounds and drug targets, within both preclinical studies and clinical trials.

EXPERT OPINION

Tolvaptan is currently the sole approved treatment option available for ADPKD patients, while no approved treatment alternatives exist for ARPKD or NPHP patients. Clinical trials are presently underway to evaluate additional medications in ADPKD and ARPKD patients. Based on preclinical models, other potential therapeutic targets for ADPKD, ARPKD, and NPHP look promising. These include molecules targeting fluid transport, cellular metabolism, ciliary signaling and cell-cycle regulation. There is a real and urgent clinical need for translational research to bring novel treatments to clinical use for all forms of renal ciliopathies to reduce kidney disease progression and prevent kidney failure.

An evaluation of setmelanotide injection for chronic weight management in adult and pediatric patients with obesity due to Bardet-Biedl syndrome

INTRODUCTION

Bardet-Biedl Syndrome (BBS) is a rare, multisystemic ciliopathy with an incidence of obesity of 89%. Mutations in genes encoding BBS proteins are linked to reduced leptin sensitivity of hypothalamic POMC neurons and reduced activation of the melanocortin-4 receptor (MC4R) pathway due to deficient α-MSH production by hypothalamic POMC neurons. The MC4R pathway is involved in controlling body weight and energy metabolism, and its disruption is linked to hyperphagia and obesity. Setmelanotide is an MC4R agonist that counteracts deficiencies in the MC4R pathway of individuals with BBS.

AREAS COVERED

Data from clinical trials were reviewed along with information available from setmelanotide's approval for treatment of obesity in people ages ≥6y with a clinical diagnosis of BBS.

EXPERT OPINION

Setmelanotide is available as a daily injectable that can be used for amelioration of obesity in people with Bardet-Biedl syndrome. Its cost is substantial, which may limit its use, but among those who respond, setmelanotide can reduce body mass dramatically and potentially improve comorbid conditions associated with obesity. Setmelanotide treatment has generally tolerable side effects, primarily injection site reactions and nausea/vomiting that generally improve with continued use; almost all people using setmelanotide experience marked skin darkening due to off-target activation of cutaneous MC1R.

Novel multi-allelic variants, two BBS2 and one PKD1 variant, of renal ciliopathies: A case report and literature review

BACKGROUND

Bardet-Biedl syndrome (BBS) and autosomal dominant polycystic kidney disease (ADPKD) are renal ciliopathies. BBS has 22 pathogenic genes, and ADPKD is mainly caused by PKD1 and PKD2 variants. Cases with tri-allelic variants of BBS and PKD1 are rare.

CASE PRESENTATION

The proband was an 11-year-old Chinese male with cysts in both kidneys, blurred vision, hyperopia, and short fingers and toes. The patient underwent a kidney transplant due to rapid deterioration of renal failure. During follow-up, a smaller field of vision, a slow increase in height, and a weight gain were observed. In addition, renal function and anemia were improved. High-throughput sequencing analysis showed two heterozygous variants in BBS2 (c.563delT (p.I188Tfs*13) inherited from the father and c.534+1G > t (splicing) from the mother) and one heterozygous variant in PKD1 (c.6223C > T (p.R2075C)) inherited from the mother.

CONCLUSION

This paper reported a ciliopathy patient with multi-allelic variants (two BBS2 variants and one PKD1 variant) that may lead to early symptoms and more rapid progression. An early genetic diagnosis may contribute to predicting disease progression and guiding management and follow-up.

Kinase Inhibitors in Genetic Diseases

Over the years, several studies have shown that kinase-regulated signaling pathways are involved in the development of rare genetic diseases. The study of the mechanisms underlying the onset of these diseases has opened a possible way for the development of targeted therapies using particular kinase inhibitors. Some of these are currently used to treat other diseases, such as cancer. This review aims to describe the possibilities of using kinase inhibitors in genetic pathologies such as tuberous sclerosis, RASopathies, and ciliopathies, describing the various pathways involved and the possible targets already identified or currently under study.

Technologies, strategies, and cautions when deconvoluting genome-wide association signals: FTO in focus

Genome-wide association studies have revealed a plethora of genetic variants that correlate with polygenic conditions. However, causal molecular mechanisms have proven challenging to fully define. Without such information, the associations are not physiologically useful or clinically actionable. By reviewing studies of the FTO locus in the genetic etiology of obesity, we wish to highlight advances in the field fueled by the evolution of technical and analytic strategies in assessing the molecular bases for genetic associations. Particular attention is drawn to extrapolating experimental findings from animal models and cell types to humans, as well as technical aspects used to identify long-range DNA interactions and their biological relevance with regard to the associated trait. A unifying model is proposed by which independent obesogenic pathways regulated by multiple FTO variants and genes are integrated at the primary cilium, a cellular antenna where signaling molecules that control energy balance convene.

High molecular diagnostic yields and novel phenotypic expansions involving syndromic anorectal malformations

Evidence suggests that genetic factors contribute to the development of anorectal malformations (ARMs). However, the etiology of the majority of ARMs cases remains unclear. Exome sequencing (ES) may be underutilized in the diagnostic workup of ARMs due to uncertainty regarding its diagnostic yield. In a clinical database of ~17,000 individuals referred for ES, we identified 130 individuals with syndromic ARMs. A definitive or probable diagnosis was made in 45 of these individuals for a diagnostic yield of 34.6% (45/130). The molecular diagnostic yield of individuals who initially met criteria for VACTERL association was lower than those who did not (26.8% vs 44.1%; p = 0.0437), suggesting that non-genetic factors may play an important role in this subset of syndromic ARM cases. Within this cohort, we identified two individuals who carried de novo pathogenic frameshift variants in ADNP, two individuals who were homozygous for pathogenic variants in BBS1, and single individuals who carried pathogenic or likely pathogenic variants in CREBBP, EP300, FANCC, KDM6A, SETD2, and SMARCA4. The association of these genes with ARMs was supported by previously published cases, and their similarity to known ARM genes as demonstrated using a machine learning algorithm. These data suggest that ES should be considered for all individuals with syndromic ARMs in whom a molecular diagnosis has not been made, and that ARMs represent a low penetrance phenotype associated with Helsmoortel-van der Aa syndrome, Bardet-Biedl syndrome 1, Rubinstein-Taybi syndromes 1 and 2, Fanconi anemia group C, Kabuki syndrome 2, SETD2-related disorders, and Coffin-Siris syndrome 4.

Adipose tissue function and insulin sensitivity in syndromic obesity of Bardet-Biedl syndrome

BACKGROUND

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive syndromic obesity of childhood onset among many other features. To date, the excess risk of metabolic complications of severe early-onset obesity in BBS remains controversial. In-depth investigation of adipose tissue structure and function with detailed metabolic phenotype has not been investigated yet.

OBJECTIVE

To investigate adipose tissue function in BBS.

DESIGN

A prospective cross-sectional study.

MAIN OUTCOME MEASURE

To determine if there are differences in insulin resistance, metabolic profile, adipose tissue function and gene expression in patients with BBS compared to BMI-matched polygenic obese controls.

METHOD

9 adults with BBS and 10 controls were recruited from the national centre for BBS, Birmingham, UK. An in-depth study of adipose tissue structure and function along with insulin sensitivity was performed using hyperinsulinemic-euglycemic clamp studies, adipose tissue microdialysis, histology and RNA sequencing, and measurement of circulating adipokines and inflammatory biomarkers.

RESULTS

Adipose tissue structure, gene expression and in vivo functional analysis between BBS and polygenic obesity cohorts were similar. Using hyperinsulinemic-euglycemic clamp and surrogate markers of insulin resistance, we found no significant differences in insulin sensitivity between BBS and obese controls. Furthermore, no significant changes were noted in an array of adipokines, cytokines, pro-inflammatory markers and adipose tissue RNA transcriptomic.

CONCLUSION

Although childhood-onset extreme obesity is a feature of BBS, detailed studies of insulin sensitivity and adipose tissue structure and function are similar to common polygenic obesity. This study adds to the literature by suggesting that it is the quality and quantity of adiposity not the duration that drives the metabolic phenotype.

Delineating the Spectrum of Genetic Variants Associated with Bardet-Biedl Syndrome in Consanguineous Pakistani Pedigrees

This study aimed to find the molecular basis of Bardet-Biedl syndrome (BBS) in Pakistani consanguineous families. A total of 12 affected families were enrolled. Clinical investigations were performed to access the BBS-associated phenotypes. Whole exome sequencing was conducted on one affected individual from each family. The computational functional analysis predicted the variants' pathogenic effects and modeled the mutated proteins. Whole-exome sequencing revealed 9 pathogenic variants in six genes associated with BBS in 12 families. The BBS6/MKS was the most common BBS causative gene identified in five families (5/12, 41.6%), with one novel (c.1226G>A, p.Gly409Glu) and two reported variants. c.774G>A, Thr259LeuTer21 was the most frequent BBS6/MMKS allele in three families 3/5 (60%). Two variants, c.223C>T, p.Arg75Ter and a novel, c. 252delA, p.Lys85STer39 were detected in the BBS9 gene. A novel 8bp deletion c.387_394delAAATAAAA, p. Asn130GlyfsTer3 was found in BBS3 gene. Three known variants were detected in the BBS1, BBS2, and BBS7 genes. Identification of novel likely pathogenic variants in three genes reaffirms the allelic and genetic heterogeneity of BBS in Pakistani patients. The clinical differences among patients carrying the same pathogenic variant may be due to other factors influencing the phenotype, including variants in other modifier genes.

T cell-specific deficiency in BBSome component BBS1 interferes with selective immune responses

Bsardet Biedl syndrome (BBS) is a genetic condition associated with various clinical features including cutaneous disorders and certain autoimmune and inflammatory diseases pointing to a potential role of BBS proteins in the regulation of immune function. BBS1 protein, which is a key component of the BBSome, a protein complex involved in the regulation of cilia function and other cellular processes, has been implicated in the immune synapse assembly by promoting the centrosome polarization to the antigen-presenting cells. Here, we assessed the effect of disrupting the BBSome, through Bbs1 gene deletion, in T cells. Interestingly, mice lacking the Bbs1 gene specifically in T cells (T-BBS1-/-) displayed normal body weight, adiposity, and glucose handling, but have smaller spleens. However, T-BBS1-/- mice had no change in the proportion and absolute number of B cells and T cells in the spleen and lymph nodes. There was also no alteration in the CD4/CD8 lineage commitment or survival in the thymus of T-BBS1-/- mice. On the other hand, T-BBS1-/- mice treated with Imiquimod dermally exhibited a significantly higher percentage of CD3-positive splenocytes that was due to CD4 but not CD8 T cell predominance. Notably, we found that T-BBS1-/- mice had significantly decreased wound closure, an effect that was more pronounced in males indicating that the BBSome plays an important role in T cell-mediated skin repair. Together, these findings implicate the BBSome in the regulation of selective functions of T cells.

Diabetes mellitus in Bardet Biedl syndrome

PURPOSE OF REVIEW

Bardet Biedl syndrome (BBS) is a rare disease characterized by obesity and hyperphagia. Despite the very high prevalence of paediatric and adult obesity in this population, the prevalence of diabetes mellitus is not well described.

RECENT FINDINGS

Studies in small and moderately large cohorts suggest a high prevalence of traditional risk factors for diabetes mellitus in people with BBS. People with BBS appear to have a high prevalence of insulin resistance and metabolic syndrome. Small cohort studies have identified high rates of sleep disordered breathing, including sleep apnoea syndrome. Recent research has characterized traditional behavioural risk factors such as sleep hygiene and physical inactivity in people with BBS. High rates of insufficient sleep and prolonged sedentary time suggest behavioural targets of interventions to treat or prevent diabetes mellitus. Hyperphagia, likely caused by defects in the hypothalamic melanocortin-4 receptor (MC4R) neuronal pathway, pose additional challenges to behavioural interventions to prevent diabetes mellitus.

SUMMARY

Understanding the prevalence of diabetes mellitus and other metabolic disorders in people with BBS and the impact of traditional risk factors on glucose regulation are important to developing effective treatments in this population.

Bardet-Biedl Syndrome: Current Perspectives and Clinical Outlook

The Bardet Biedl syndrome (BBS) is a rare inherited disorder considered a model of non-motile ciliopathy. It is in fact caused by mutations of genes encoding for proteins mainly localized to the base of the cilium. Clinical features of BBS patients are widely shared with patients suffering from other ciliopathies, especially autosomal recessive syndromic disorders; moreover, mutations in cilia-related genes can cause different clinical ciliopathy entities. Besides the best-known clinical features, as retinal degeneration, learning disabilities, polydactyly, obesity and renal defects, several additional clinical signs have been reported in BBS, expanding our understanding of the complexity of its clinical spectrum. The present review aims to describe the current knowledge of BBS i) pathophysiology, ii) clinical manifestations, highlighting both the most common and the less described features, iii) current and future perspective for treatment.

Quality of life improvements following one year of setmelanotide in children and adult patients with Bardet-Biedl syndrome: phase 3 trial results

BACKGROUND

Bardet-Biedl syndrome is a rare genetic disease associated with hyperphagia and early-onset, severe obesity. There is limited evidence on how hyperphagia and obesity affect health-related quality of life in patients with Bardet-Biedl syndrome, and on how management of these symptoms may influence disease burden. This analysis evaluated changes in health-related quality of life in adults and children with Bardet-Biedl syndrome in a Phase 3 trial following 1 year of setmelanotide treatment (ClinicalTrials.gov identifier: NCT03746522).

METHODS

Patients with Bardet-Biedl syndrome and obesity received 52 weeks of treatment with setmelanotide and completed various self-reported health-related quality of life measures. Patients aged < 18 years or their caregiver completed the Pediatric Quality of Life Inventory (PedsQL; meaningful improvement, 4.4-point change); adults aged ≥ 18 years completed the Impact of Weight on Quality of Life Questionnaire-Lite (IWQOL-Lite; meaningful improvement range, 7.7-12-point change). Descriptive outcomes were reported in patients with data both at active treatment baseline and after 52 weeks of treatment.

RESULTS

Twenty patients (< 18 years, n = 9; ≥ 18 years, n = 11) reported health-related quality of life at baseline and 52 weeks. For children and adolescents, PedsQL score mean change from baseline after 52 weeks was + 11.2; all patients with PedsQL impairment at baseline (n = 4) experienced clinically meaningful improvement. In adults, IWQOL-Lite score mean change from baseline was + 12.0. Of adults with IWQOL-Lite impairment at baseline (n = 8), 62.5% experienced clinically meaningful improvement. In adults, IWQOL-Lite score was significantly correlated with changes in percent body weight (P = 0.0037) and body mass index (P = 0.0098).

CONCLUSIONS

After 1 year of setmelanotide, patients reported clinically meaningful improvements across multiple health-related quality of life measures. This study highlights the need to address the impaired health-related quality of life in Bardet-Biedl syndrome, and supports utility of setmelanotide for reducing this burden. Trial Registration NCT03746522. Registered November 19, 2018, https://clinicaltrials.gov/ct2/show/NCT03746522 .

Bangladeshi Case Series of Bardet-Biedl Syndrome

A rare multisystemic, ciliopathic autosomal recessive disorder called Bardet-Biedl syndrome (BBS) primarily affects children of consanguineous marriages. Both men and women are affected by it. It is characterized by some major and many minor features to aid in the clinical diagnosis and management. Here, we reported two Bangladeshi patients (a 9-year-old girl and 24-year-old male) who were presented with various major and minor features of BBS. Both patients came to us with the symptoms including excessive weight gain, poor vision, and learning disabilities with polydactyly. Our case 1 presented four primary features (retinal degenerations, polydactyly, obesity, and learning deficits) and six secondary features (behavioral abnormality, delayed development, diabetes mellitus, diabetes insipidus, brachydactyly, and LVH), whereas case 2 presented five major criteria (truncal obesity, polydactyly, retinal dystrophy, learning disabilities, and hypogonadism) and six minor criteria (strabismus and cataract, delay in speech, behavioral disorder, developmental delay, brachydactyly and syndactyly, and impaired glucose tolerance test). We diagnosed the cases as BBS. Because there is no specific treatment for BBS, we highlighted the importance of diagnosing it as early as possible so that comprehensive and multidisciplinary care can be offered to prevent avoidable morbidity and mortality.

Clinical and molecular diagnosis of Bardet-Biedl syndrome (BBS)

Bardet-Biedl syndrome (BBS) is a rare genetic disease of the group of ciliopathies, a group of pathologies characterized mainly by defects in the structure and/or function of primary cilia. The main features of this ciliopathy are retinal dystrophy, obesity, polydactyly, urogenital and renal abnormalities, and cognitive impairment, commonly accompanied by various secondary features, making clear the extensive clinical heterogeneity associated with this syndrome, which, together with the frequent overlapping phenotype with other ciliopathies, greatly complicates its diagnosis. Patients are mainly detected by their pediatrician at quite early ages, usually between 2 and 6years. The pediatrician, given the main symptoms they present, usually refers patients to a specialist. Personalized medicine brought diagnosis closer to many patients who lacked it. It usually presents an autosomal recessive mode of inheritance, but in recent years several authors have proposed more complex inheritance models to explain the frequent inter- and intra-familial clinical variability. The main molecular techniques used for diagnosis are gene panels, the clinical exome and, in certain cases, the patient's complete genome. Although numerous studies have contributed to defining the role of the different BBS genes and designing various strategies for the molecular diagnosis of BBS, as well as delving into the functions performed by these proteins, these advances have not been sufficient to develop a complete treatment for this syndrome. and to be able to offer patients some therapeutic options.

A Japanese boy with Bardet-Biedl syndrome caused by a novel homozygous variant in the ARL6 gene who was initially diagnosed with retinitis punctata albescens: A case report

PURPOSE

Bardet-Biedl Syndrome (BBS) is an autosomal recessive systemic disorder characterized by retinitis pigmentosa, polydactyly, obesity, intellectual disability, renal impairments, and hypogonadism. The purpose of this study was to determine the ocular characteristics of a boy with BBS caused by a novel homozygous variant in the ARL6 (alternative named BBS3) gene who had been originally diagnosed with retinitis punctata albescens.

METHODS

This was an observational case study. The patient underwent ophthalmological examinations, electroretinography, and genetic analyses using whole-exome sequencing.

RESULTS

A 7-year-old boy was examined in our hospital with complaints of a progressive reduction of his visual acuity and night blindness in both eyes. There was no family history of eye diseases and no consanguineous marriage. Fundus examinations showed numerous white spots in the deep retina and retinal pigment epithelium. Fundus autofluorescence showed hypofluorescence consistent with these spots. Both the scotopic and photopic components of the full-field electroretinographies were non-detectable. Based on these clinical findings, this boy was suspected to have retinitis punctata albescens. Subsequent genetic testing using whole-exome sequencing revealed a novel homozygous variants in the ARL6/BBS3 gene (NM_001278293.3:c.528G>A, (p.Trp176Ter)). A systemic examination by the pediatric department revealed that this boy had a history of a surgical excision of polydactyly on his left foot when he was born, and that he was mildly obese. There were no prominent intellectual or gonadal dysfunctions, no craniofacial or dental abnormalities, no congenital heart disease, and no hearing impairment. He was then clinically and genetically diagnosed with BBS.

CONCLUSION AND IMPORTANCE

In children with night blindness and progressive visual dysfunction, it is important for ophthalmologists to consult clinical geneticists and pediatricians to rule out the possibility of systemic diseases such as BBS.

Ciliary control of adipocyte progenitor cell fate regulates energy storage

The primary cilium is a cellular sensory organelle found in most cells in our body. This includes adipocyte progenitor cells in our adipose tissue, a complex organ involved in energy storage, endocrine signaling, and thermogenesis. Numerous studies have shown that the primary cilium plays a critical role in directing the cell fate of adipocyte progenitor cells in multiple adipose tissue types. Accordingly, diseases with dysfunctional cilia called ciliopathies have a broad range of clinical manifestations, including obesity and diabetes. This review summarizes our current understanding of how the primary cilium regulates adipocyte progenitor cell fate in multiple contexts and illustrates the importance of the primary cilium in regulating energy storage and adipose tissue function.

Bardet–Biedl Syndrome: A Brief Overview on Clinics and Genetics

Bardet–Biedl syndrome is a genetically pleiotropic disorder characterized by high clinical heterogeneity with severe multiorgan impairment. Clinically, it encompasses primary and secondary manifestations, mainly including retinal dystrophy, mental retardation, obesity, polydactyly, hypogonadism in male, and renal abnormalities. At least 21 different genes have been identified, all involved into primary cilium structure or function. To date, genotype–phenotype correlation is still poor.

Identification of bone metabolism disorders in patients with Alström and Bardet-Biedl syndromes based on markers of bone turnover and mandibular atrophy

Objectives

Causative variants in genes responsible for Alström syndrome (ALMS) and Bardet-Biedl syndrome (BBS) cause damage to primary cilia associated with correct functioning of cell signaling pathways in many tissues. Despite differences in genetic background, both syndromes affect multiple organs and numerous clinical manifestations are common including obesity, retinal degeneration, insulin resistance, type 2 diabetes and many others. The aim of the study was to evaluate bone metabolism abnormalities and their relation to metabolic disorders based on bone turnover markers and presence of mandibular atrophy in patients with ALMS and BBS syndromes.

Material and methods

In 18 patients (11 with ALMS and 7 with BBS aged 5–29) and in 42 age-matched (p < 0.05) healthy subjects, the following markers of bone turnover were assessed: serum osteocalcin (OC), osteoprotegerin (OPG), s-RANKL and urinary deoxypyridinoline - DPD. In addition, a severity of alveolar atrophy using dental panoramic radiograms was evaluated.

Results

Lower serum OC (p = 0.0004) and urinary DPD levels (p = 0.0056) were observed in the study group compared to controls. In ALMS and BBS patients, serum OC and urinary DPD values negatively correlated with the HOMA-IR index, while a positive correlation between the OC and 25-OHD levels and a negative correlation between s-RANKL and fasting glucose concentrations were found. A significant difference in the incidence of low-grade mandibular atrophy between patients with ALMS and BBS and controls (p < 0.0001) was observed.

Conclusions

The identification of bone metabolism disorders in patients with ALMS and BBS syndromes indicates the necessity to provide them with appropriate diagnosis and treatment of these abnormalities.

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Bone metabolism disorders in Alstrom and Bardet-Biedl syndromes

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Markers of bone turnover in Alstrom and Bardet-Biedl syndromes

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Mandibular atrophy in Alstrom and Bardet-Biedl syndromes

Efficacy and safety of setmelanotide, a melanocortin-4 receptor agonist, in patients with Bardet-Biedl syndrome and Alström syndrome: a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial with an open-label period

BACKGROUND

Impaired cilial signalling in the melanocortin-4 receptor (MC4R) pathway might contribute to obesity in patients with Bardet-Biedl syndrome and Alström syndrome, rare genetic diseases associated with hyperphagia and early-onset severe obesity. We aimed to evaluate the effect of setmelanotide on bodyweight in these patients.

METHODS

This multicentre, randomised, 14-week double-blind, placebo-controlled, phase 3 trial followed by a 52-week open-label period, was performed at 12 sites (hospitals, clinics, and universities) in the USA, Canada, the UK, France, and Spain. Patients aged 6 years or older were included if they had a clinical diagnosis of Bardet-Biedl syndrome or Alström syndrome and obesity (defined as BMI >97th percentile for age and sex for those aged 6-15 years and ≥30 kg/m2 for those aged ≥16 years). Patients were randomly assigned (1:1) using a numerical randomisation code to receive up to 3·0 mg of subcutaneous setmelanotide or placebo once per day during the 14-week double-blind period, followed by open-label setmelanotide for 52 weeks. The primary endpoint, measured in the full analysis set, was the proportion of patients aged 12 years or older who reached at least a 10% reduction in bodyweight from baseline after 52 weeks of setmelanotide treatment. This study is registered with ClinicalTrials.gov, NCT03746522.

FINDINGS

Between Dec 10, 2018, and Nov 25, 2019, 38 patients were enrolled and randomly assigned to receive setmelanotide (n=19) or placebo (n=19; 16 with Bardet-Biedl syndrome and three with Alström syndrome in each group). In terms of the primary endpoint, 32·3% (95% CI 16·7 to 51·4; p=0·0006) of patients aged 12 years or older with Bardet-Biedl syndrome reached at least a 10% reduction in bodyweight after 52 weeks of setmelanotide. The most commonly reported treatment-emergent adverse events were skin hyperpigmentation (23 [61%] of 38) and injection site erythema (18 [48%]). Two patients had four serious adverse events (blindness, anaphylactic reaction, and suicidal ideation); none were considered related to setmelanotide treatment.

INTERPRETATION

Setmelanotide resulted in significant bodyweight reductions in patients with Bardet-Biedl syndrome; however, these results were inconclusive in patients with Alström syndrome. These results support the use of setmelanotide and provided the necessary evidence for approval of this drug as the first treatment for obesity in patients with Bardet-Biedl syndrome.

FUNDING

Rhythm Pharmaceuticals.

Behavioral Phenotyping of Bbs6 and Bbs8 Knockout Mice Reveals Major Alterations in Communication and Anxiety

The primary cilium is an organelle with a central role in cellular signal perception. Mutations in genes that encode cilia-associated proteins result in a collection of human syndromes collectively termed ciliopathies. Of these, the Bardet-Biedl syndrome (BBS) is considered one of the archetypical ciliopathies, as patients exhibit virtually all respective clinical phenotypes, such as pathological changes of the retina or the kidney. However, the behavioral phenotype associated with ciliary dysfunction has received little attention thus far. Here, we extensively characterized the behavior of two rodent models of BBS, Bbs6/Mkks, and Bbs8/Ttc8 knockout mice concerning social behavior, anxiety, and cognitive abilities. While learning tasks remained unaffected due to the genotype, we observed diminished social behavior and altered communication. Additionally, Bbs knockout mice displayed reduced anxiety. This was not due to altered adrenal gland function or corticosterone serum levels. However, hypothalamic expression of Lsamp, the limbic system associated protein, and Adam10, a protease acting on Lsamp, were reduced. This was accompanied by changes in characteristics of adult hypothalamic neurosphere cultures. In conclusion, we provide evidence that behavioral changes in Bbs knockout mice are mainly found in social and anxiety traits and might be based on an altered architecture of the hypothalamus.

Novel mutations in BBS genes and clinical characterization of Chinese families with Bardet-Biedl syndrome

PURPOSE

Bardet-Biedl syndrome (BBS) is a rare autosomal-recessive inherited disorder characterized by multisystem anomalies. The objective of this study was to detect and analyse pathogenic variants in four Chinese families with BBS.

METHODS

Comprehensive clinical examinations were performed to investigate and evaluate the phenotypes of the affected individuals from four families. Genomic DNA was extracted from peripheral blood. Next-generation sequencing (NGS) was performed for four families, and the presence of pathogenic variants was confirmed via Sanger sequencing.

RESULTS

There were two males and three females with a mean age of 16.00 years. All probands displayed the primary clinical features of BBS. Mutation screening demonstrated four novel mutations: c.613C>T; p.Q205* in the BBS5 gene, c.1391C>G; p.S464* in the BBS10 gene, and c.155delC; p.S52* and c.1584T>G; p.Y528* in the BBS12 gene. Two previously reported mutations were also identified, including c.534 + 1G>T in the BBS2 gene and c.539G>A; p.G180E in the BBS10 gene. The bioinformatic analysis revealed that all the detected mutations in BBS genes were disease causing.

CONCLUSIONS

This study identified four novel BBS gene mutations in these Chinese families and further expanded the genotypic spectrum of BBS, thus contributing to the literature and understanding of this multisystem disease.

Bardet-Biedl Syndrome Presenting in Adulthood

Bardet-Biedl syndrome (BBS) is a rare disorder with a frequency of 1:1,60,000. The disease is inherited in an autosomal recessive manner. Less than 15 cases have been reported from India. We present a case of Bardet-Biedl syndrome presenting to the medical emergency with acute breathlessness because of de-compensated renal failure and salient features such as marked polydactyly, central obesity, retinitis pigmentosa, end-stage renal diseases, and mental retardation. Genetic study showed that the patient had BBS genetic variant 9 (MIM#615896), VUS variant. The patient was primarily treated for end-stage chronic renal failure with hemodialysis. We are reporting this case for its rarity and the presence of a novel genetic variant of an unidentified significance as per genome mapping. BBS is often not diagnosed at all or diagnosed late until end-stage renal failure sets in. Timely diagnosis might not help treat the condition but surely improve the quality of life for the patient.

Computational and Structural Analysis to Assess the Pathogenicity of Bardet-Biedl Syndrome Related Missense Variants Identified in Bardet-Biedl Syndrome 10 Gene (BBS10)

Bardet-Biedl Syndrome (BBS) is a rare inherited disorder resulting in multiple organ dysfunctions, whose cardinal clinical features include cognitive impairment, obesity, and renal dysfunction. Although it is highly heterogeneous at genetic levels, BBS10 is one of the major causative genes worldwide. The BBS10 protein is part of a multiprotein complex localized at the basal body of the primary cilium. With the advancement of sequencing technologies, novel missense mutations are regularly reported in BBS10. However, prioritizing missense variants and conducting further in-depth analysis are key challenges in addressing their pathogenic effect. This study aims to characterize the known missense mutations of BBS10 by combining nine different in silico tools (SIFT, SNAP2, PROVEAN, Align-GVGD, ConSurf, I Mutant, MuPro, PremPS, and Dynamut) and molecular dynamics (MD) simulations. A total of 101 BBS10 missense variants have been analyzed. Our results showed that six BBS10 missense variants (Ser191Leu, Cys19Gly, Ile342Thr, Cys371Ser, Ala417Glu, and Tyr613Cys) were potentially deleterious. Overall, this study provides a comprehensive workflow for screening BBS10 missense mutations to identify pathogenic variants effectively.

Hypogonadism in Males With Genetic Neurodevelopmental Syndromes

Genetic syndromes that affect the nervous system may also disrupt testicular function, and the mechanisms for these effects may be interrelated. Most often neurological signs and symptoms predominate and hypogonadism remains undetected and untreated, while in other cases, a thorough evaluation of a hypogonadal male reveals previously unrecognized ataxia, movement disorder, muscle weakness, tremor, or seizures, leading to a syndromic diagnosis. Androgen deficiency in patients with neurological diseases may aggravate muscle weakness and fatigue and predispose patients to osteoporosis and obesity. The purpose of this mini review is to provide a current understanding of the clinical, biochemical, histologic, and genetic features of syndromes in which male hypogonadism and neurological dysfunction may coexist and may be encountered by the clinical endocrinologist.

Monitoring and Management of Bardet-Biedl Syndrome: What the Multi-Disciplinary Team Can Do

Bardet – Biedl syndrome is a rare autosomal recessive multisystem non-motile ciliopathy. It has heterogeneous clinical manifestations. It is caused by mutations in 26 genes encoding BBSome proteins, chaperonines, and IFT complex. The main clinical features are: retinal cone-rod dystrophy, central obesity, postaxial polydactyly, cognitive impairment, hypogonadism and genitourinary anomalies, and kidney disease. The onset of clinical manifestations is variable which makes the diagnosis difficult in some patients. Because of the multiple system involvement, a multidisciplinary approach is necessary. The purpose of this review is to provide monitoring and management directions for a better approach to these patients.

Genetics behind Cerebral Disease with Ocular Comorbidity: Finding Parallels between the Brain and Eye Molecular Pathology

Cerebral visual impairments (CVIs) is an umbrella term that categorizes miscellaneous visual defects with parallel genetic brain disorders. While the manifestations of CVIs are diverse and ambiguous, molecular diagnostics stand out as a powerful approach for understanding pathomechanisms in CVIs. Nevertheless, the characterization of CVI disease cohorts has been fragmented and lacks integration. By revisiting the genome-wide and phenome-wide association studies (GWAS and PheWAS), we clustered a handful of renowned CVIs into five ontology groups, namely ciliopathies (Joubert syndrome, Bardet-Biedl syndrome, Alstrom syndrome), demyelination diseases (multiple sclerosis, Alexander disease, Pelizaeus-Merzbacher disease), transcriptional deregulation diseases (Mowat-Wilson disease, Pitt-Hopkins disease, Rett syndrome, Cockayne syndrome, X-linked alpha-thalassaemia mental retardation), compromised peroxisome disorders (Zellweger spectrum disorder, Refsum disease), and channelopathies (neuromyelitis optica spectrum disorder), and reviewed several mutation hotspots currently found to be associated with the CVIs. Moreover, we discussed the common manifestations in the brain and the eye, and collated animal study findings to discuss plausible gene editing strategies for future CVI correction.

Multi-Omics Studies Unveil Extraciliary Functions of BBS10 and Show Metabolic Aberrations Underlying Renal Disease in Bardet-Biedl Syndrome

Bardet–Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy resulting in multiple organ dysfunctions, including chronic kidney disease (CKD). Despite the recent progress in the ’ciliopathy’ field, there is still little information on the mechanisms underlying renal disease. To elucidate these pathomechanisms, we conducted a translational study, including (i) the characterization of the urine metabolomic pattern of BBS patients and controls in a pilot and confirmation study and (ii) the proteomic analysis of the BBS10 interactome, one of the major mutated BBS genes in patients, in a renal-epithelial-derived cell culture model. The urine metabolomic fingerprinting of BBS patients differed from controls in both pilot and confirmation studies, demonstrating an increased urinary excretion of several monocarboxylates, including lactic acid (LA), at both early and late CKD stages. Increased urine LA was detected in the absence of both increased plasmatic LA levels and generalized proximal tubular dysfunction, suggesting a possible renal-specific defective handling. The inner medulla renal epithelial (IMCD3) cell line, where Bbs10 was stably invalidated, displayed an increased proliferative rate, increased ATP production, and an up-regulation of aerobic glycolysis. A mass spectrometry-based analysis detected several putative BBS10 interactors in vitro, indicating a potential role of BBS10 in several biological processes, including renal metabolism, RNA processing, and cell proliferation. The present study suggests that the urine metabolomic pattern of BBS patients may reflect intra-renal metabolic aberrations. The analysis of BBS10 interactors unveils possible novel functions, including cell metabolism.

Novel homozygous nonsense mutation associated with Bardet-Biedl syndrome in fetuses with congenital renal malformation

BACKGROUND

The Bardet-Biedl syndrome (BBS) is a rare autosomal recessive disorder, characterized by clinical and genetic heterogeneity. BBS is more commonly reported in adults and children than in fetuses. Here, a retrospective study on 210 fetuses with congenital renal malformation was conducted.

METHODS

The fetuses were diagnosed using invasive prenatal tests, including chromosome karyotype analysis, whole exome sequencing (WES), and single-nucleotide polymorphism array. We found the intrauterine phenotype of a fetus presenting enlarged kidneys, enhanced echo, and oligohydramnios; therefore, the fetus was characterized to have BBS.

RESULTS

Chromosome karyotype analysis presented normal results. Analysis using an Affymetrix CytoScan 750K array revealed 2 homozygous regions. However, WES revealed a homozygous mutation of c.1177C>T (p.Arg393*) on exon 12 of BBS1 and a heterozygous variation of c.2704G>A (p.Asp902Asn) on exon 22 of CC2D2A. The American College of Medical Genetics and Genomics guidelines identified c.1177C>T and c.2704G>A as a pathogenic mutation and of uncertain significance, respectively. Sanger sequencing identified heterozygous mutation, that is, c.1177C>T and heterozygous variation, that is, c.2704G>A in the parents of the fetus.

CONCLUSIONS

WES identified a novel homozygous nonsense mutation c.1177C>T in BBS1 of a Chinese fetus with congenital renal malformation. This finding provides insight into the BBS1 mutations in Asian populations in general and shows the necessity of genetic counseling.

Central precocious puberty occurring in Bardet‑Biedl syndrome‑10 as a method for self‑protection of human reproductive function: A case report

Hypogonadism and obesity are primary features of Bardet-Biedl syndrome (BBS). Obesity is also an associated factor of central precocious puberty (CPP). The present report describes the case of a girl (age, 7 years and 6 months), with clinical manifestations of precocious puberty, progressive obesity, postaxial polydactyly, retinal degeneration and intellectual disability. The patient visited the clinic for the first time due to early breast development and progressive obesity. After 8 months of follow-up, the bone age had advanced almost 3 years, and the gonadotropin-releasing hormone (GnRH) stimulation test showed results that had changed from indicating pseudo precocious puberty to CPP. Whole-exome gene sequencing showed that there were two heterozygous mutations in the BBS type 10 (BBS10) gene, chr12:76739816(c.1949del) and chr12:76740374(c.1391C>G). The final diagnosis was of BBS10 and CPP. In order to protect the reproductive capacity of the patient, GnRH analogs were used for CPP treatment. After 15 months of treatment and follow-up, a physical examination revealed Tanner breast stage 1. Ultrasonography showed that the uterus and ovaries had reduced to their prepubertal size. In conclusion, the present report describes a case of CPP that occurred in a young girl with BBS10. We hypothesize that this was a prelude to gonad dysplasia, acting as a method for the self-protection of human reproductive function. However, more clinical data and molecular biological evidence are required to confirm the etiology and mechanism of this case.

Ophthalmic and Genetic Features of Bardet Biedl Syndrome in a German Cohort

The aim of this study was to characterize the ophthalmic and genetic features of Bardet Biedl (BBS) syndrome in a cohort of patients from a German specialized ophthalmic care center. Sixty-one patients, aged 5−56 years, underwent a detailed ophthalmic examination including visual acuity and color vision testing, electroretinography (ERG), visually evoked potential recording (VEP), fundus examination, and spectral domain optical coherence tomography (SD-OCT). Adaptive optics flood illumination ophthalmoscopy was performed in five patients. All patients had received diagnostic genetic testing and were selected upon the presence of apparent biallelic variants in known BBS-associated genes. All patients had retinal dystrophy with morphologic changes of the retina. Visual acuity decreased from ~0.2 (decimal) at age 5 to blindness 0 at 50 years. Visual field examination could be performed in only half of the patients and showed a concentric constriction with remaining islands of function in the periphery. ERG recordings were mostly extinguished whereas VEP recordings were reduced in about half of the patients. The cohort of patients showed 51 different likely biallelic mutations—of which 11 are novel—in 12 different BBS-associated genes. The most common associated genes were BBS10 (32.8%) and BBS1 (24.6%), and by far the most commonly observed variants were BBS10 c.271dup;p.C91Lfs*5 (21 alleles) and BBS1 c.1169T>G;p.M390R (18 alleles). The phenotype associated with the different BBS-associated genes and genotypes in our cohort is heterogeneous, with diverse features without genotype−phenotype correlation. The results confirm and expand our knowledge of this rare disease.

Recurrent pericarditis in a patient with Bardet-Biedl syndrome: A case report

Bardet-Biedl syndrome is a rare autosomal recessive disorder characterized by rod-cone dystrophy, renal dysfunction, obesity, learning difficulties, hypogonadism, polydactyl, and many other minor features that can affect the cardiovascular, locomotive, neurological, and endocrine systems. We report the case of a 16-year-old boy affected by Bardet-Biedl syndrome who presented with recurrent pericarditis with an optimal response to treatment with Anakinra. To our knowledge, this is the first description of an association between Bardet-Biedl syndrome and recurrent pericarditis.

On the Wrong Track: Alterations of Ciliary Transport in Inherited Retinal Dystrophies

Ciliopathies are a group of heterogeneous inherited disorders associated with dysfunction of the cilium, a ubiquitous microtubule-based organelle involved in a broad range of cellular functions. Most ciliopathies are syndromic, since several organs whose cells produce a cilium, such as the retina, cochlea or kidney, are affected by mutations in ciliary-related genes. In the retina, photoreceptor cells present a highly specialized neurosensory cilium, the outer segment, stacked with membranous disks where photoreception and phototransduction occurs. The daily renewal of the more distal disks is a unique characteristic of photoreceptor outer segments, resulting in an elevated protein demand. All components necessary for outer segment formation, maintenance and function have to be transported from the photoreceptor inner segment, where synthesis occurs, to the cilium. Therefore, efficient transport of selected proteins is critical for photoreceptor ciliogenesis and function, and any alteration in either cargo delivery to the cilium or intraciliary trafficking compromises photoreceptor survival and leads to retinal degeneration. To date, mutations in more than 100 ciliary genes have been associated with retinal dystrophies, accounting for almost 25% of these inherited rare diseases. Interestingly, not all mutations in ciliary genes that cause retinal degeneration are also involved in pleiotropic pathologies in other ciliated organs. Depending on the mutation, the same gene can cause syndromic or non-syndromic retinopathies, thus emphasizing the highly refined specialization of the photoreceptor neurosensory cilia, and raising the possibility of photoreceptor-specific molecular mechanisms underlying common ciliary functions such as ciliary transport. In this review, we will focus on ciliary transport in photoreceptor cells and discuss the molecular complexity underpinning retinal ciliopathies, with a special emphasis on ciliary genes that, when mutated, cause either syndromic or non-syndromic retinal ciliopathies.

Identification of a Novel Homozygous Missense (c.443A>T:p.N148I) Mutation in BBS2 in a Kashmiri Family with Bardet-Biedl Syndrome

Background

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive inherited disorder with distinctive clinical feature such as obesity, degeneration of retina, polydactyly, and renal abnormalities. The study was aimed at finding out the disease-causing variant/s in patients exhibiting clinical features of BBS.

Methods

The identification of disease-causing variant was done by using whole exome sequencing on Illumina HiSeq 4000 platform involving the SeqCap EZ Exome v3 kit (Roche NimbleGen). The identified variant was further validated by Sanger sequencing.

Results

WES revealed a novel homozygous missense mutation (NM_031885: c.443A>T:p.N148I) in exon 3 of the BBS2 gene. Sanger sequencing confirmed this variant as homozygous in both affected subjects and heterozygous in obligate parents, demonstrating autosomal recessive inheritance pattern. To the best of our knowledge, this variant was not present in literature and all publically available databases. The candidate variant is predicted to be pathogenic by a set of in-silico softwares.

Conclusion

Clinical and genetic spectrum of BBS and BBS-like disorders is not completely defined in the Pakistani as well as in Kashmiri population. Therefore, more comprehensive genetic studies are required to gain insights into genotype-phenotype associations to facilitate carrier screening and genetic counseling of families with such disorders.

Next-Generation Sequencing in the Diagnosis of Patients with Bardet-Biedl Syndrome-New Variants and Relationship with Hyperglycemia and Insulin Resistance

Bardet-Biedl syndrome (BBS) is a rare autosomal recessively inherited disease with major clinical symptoms such as: obesity, retinal degeneration, polydactyly and renal abnormalities. The aim of the study was to assess the spectrum of gene variants among patients with BBS, identified on the basis of nationwide genetic studies of monogenic diabetes in Polish population. Out of 575 patients enrolled for genetic testing from February 2017 to July 2019, 25 patients with a clinical suspicion of BBS were selected. The identification of pathogenic variants was performed by using targeted next-generation sequencing (NGS) on Illumina NextSeq 550 platform involving the SureSelect assay (Agilent, Santa Clara, CA, USA). BBS was genetically confirmed in 10 of 25 suspected patients. In patients, 14 different variants were found in six genes, mainly in BBS9 and BBS10 gene, including two novel variants. A strong association between hyperglycemia and insulin resistance in patients and the presence of variants in BBS9 gene was observed. Identification of 14 variants, including two new mutations using the NGS method, is the first molecular characteristic of Polish patients with Bardet–Biedl syndrome. It gives hope for earlier proper diagnosis of BBS in future patients selected from children with early childhood obesity and their medical multidisciplinary care.

Novel Sex Chromosomes in 3 Cichlid Fishes from Lake Tanganyika

African cichlids are well known for their adaptive radiations, but it is now apparent that they also harbor an extraordinary diversity of sex chromosome systems. In this study, we sequenced pools of males and females from species in 3 different genera of cichlids from Lake Tanganyika. We then searched for regions that were differentiated following the patterns expected for sex chromosomes. We report 2 novel sex chromosomes systems, an XY system on LG19 in Tropheus sp. "black" and a ZW system on LG7 in Hemibates stenosoma. We also identify a ZW system on LG5 in Cyprichromis leptosoma that may be convergent with a system previously described in Lake Malawi cichlids. Our data also identify candidate single nucleotide polymorphisms for the blue/yellow tail color polymorphism observed among male C. leptosoma.

A rare case of Bardet-Biedl syndrome

We report here a rare case of Bardet-Biedl syndrome (BBS). A 7-year-old boy was diagnosed to have BBS based on the clinical features: retinitis pigmentosa sine pigmento, obesity, postaxial polydactyly, syndactyly, and hypogenitalism. It was associated with mild hepatomegaly with deranged liver function test and mild renal involvement radiologically, high-arched palate, and low intelligence quotient. The patient was prescribed proper refractive correction and subjected to multidisciplinary management. BBS has ocular and systemic manifestations, requiring a multidisciplinary approach to treatment.

Bardet-Biedl Syndrome in rhesus macaques: A nonhuman primate model of retinitis pigmentosa

The development of therapies for retinal disorders is hampered by a lack of appropriate animal models. Higher nonhuman primates are the only animals with retinal structure similar to humans, including the presence of a macula and fovea. However, few nonhuman primate models of genetic retinal disease are known. We identified a lineage of rhesus macaques with a frameshift mutation in exon 3 of the BBS7 gene c.160delG (p.Ala54fs) that is predicted to produce a non-functional protein. In humans, mutations in this and other BBS genes cause Bardet-Biedl syndrome, a ciliopathy and a syndromic form of retinitis pigmentosa generally occurring in conjunction with kidney dysfunction, polydactyly, obesity, and/or hypogonadism. Three full- or half-sibling monkeys homozygous for the BBS7 c.160delG variant, at ages 3.5, 4 and 6 years old, displayed a combination of severe photoreceptor degeneration and progressive kidney disease. In vivo retinal imaging revealed features of severe macular degeneration, including absence of photoreceptor layers, degeneration of the retinal pigment epithelium, and retinal vasculature atrophy. Electroretinography in the 3.5-year-old case demonstrated loss of scotopic and photopic a-waves and markedly reduced and delayed b-waves. Histological assessments in the 4- and 6-year-old cases confirmed profound loss of photoreceptors and inner retinal neurons across the posterior retina, with dramatic thinning and disorganization of all cell layers, abundant microglia, absent or displaced RPE cells, and significant gliosis in the subretinal space. Retinal structure, including presence of photoreceptors, was preserved only in the far periphery. Ultrasound imaging of the kidneys revealed deranged architecture, and renal histopathology identified distorted contours with depressed, fibrotic foci and firmly adhered renal capsules; renal failure occurred in the 6-year-old case. Magnetic resonance imaging obtained in one case revealed abnormally low total brain volume and unilateral ventricular enlargement. The one male had abnormally small testes at 4 years of age, but polydactyly and obesity were not observed. Thus, monkeys homozygous for the BBS7 c.160delG variant closely mirrored several key features of the human BBS syndrome. This finding represents the first identification of a naturally-occurring nonhuman primate model of BBS, and more broadly the first such model of retinitis pigmentosa and a ciliopathy with an associated genetic mutation. This important new preclinical model will provide the basis for better understanding of disease progression and for the testing of new therapeutic options, including gene and cell-based therapies, not only for BBS but also for multiple forms of photoreceptor degeneration.

Increased Expression of Lipid Metabolism Genes in Early Stages of Wooden Breast Links Myopathy of Broilers to Metabolic Syndrome in Humans

Wooden breast is a muscle disorder affecting modern commercial broiler chickens that causes a palpably firm pectoralis major muscle and severe reduction in meat quality. Most studies have focused on advanced stages of wooden breast apparent at market age, resulting in limited insights into the etiology and early pathogenesis of the myopathy. Therefore, the objective of this study was to identify early molecular signals in the wooden breast transcriptional cascade by performing gene expression analysis on the pectoralis major muscle of two-week-old birds that may later exhibit the wooden breast phenotype by market age at 7 weeks. Biopsy samples of the left pectoralis major muscle were collected from 101 birds at 14 days of age. Birds were subsequently raised to 7 weeks of age to allow sample selection based on the wooden breast phenotype at market age. RNA-sequencing was performed on 5 unaffected and 8 affected female chicken samples, selected based on wooden breast scores (0 to 4) assigned at necropsy where affected birds had scores of 2 or 3 (mildly or moderately affected) while unaffected birds had scores of 0 (no apparent gross lesions). Differential expression analysis identified 60 genes found to be significant at an FDR-adjusted p-value of 0.05. Of these, 26 were previously demonstrated to exhibit altered expression or genetic polymorphisms related to glucose tolerance or diabetes mellitus in mammals. Additionally, 9 genes have functions directly related to lipid metabolism and 11 genes are associated with adiposity traits such as intramuscular fat and body mass index. This study suggests that wooden breast disease is first and foremost a metabolic disorder characterized primarily by ectopic lipid accumulation in the pectoralis major.

Loss of Bardet-Biedl syndrome proteins causes synaptic aberrations in principal neurons

Bardet-Biedl syndrome (BBS), a ciliopathy, is a rare genetic condition characterised by retinal degeneration, obesity, kidney failure, and cognitive impairment. In spite of progress made in our general understanding of BBS aetiology, the molecular and cellular mechanisms underlying cognitive impairment in BBS remain elusive. Here, we report that the loss of BBS proteins causes synaptic dysfunction in principal neurons, providing a possible explanation for the cognitive impairment phenotype observed in BBS patients. Using synaptosomal proteomics and immunocytochemistry, we demonstrate the presence of Bbs proteins in the postsynaptic density (PSD) of hippocampal neurons. Loss of Bbs results in a significant reduction of dendritic spines in principal neurons of Bbs mouse models. Furthermore, we show that spine deficiency correlates with events that destabilise spine architecture, such as impaired spine membrane receptor signalling, known to be involved in the maintenance of dendritic spines. Our findings suggest a role for BBS proteins in dendritic spine homeostasis that may be linked to the cognitive phenotype observed in BBS.

A rare case of obesity. Can it be Bardet-Biedl Syndrome?

Bardet-Biedl Syndrome (BBS) is a rare autosomal recessive disorder with a wide spectrum of clinical manifestations like retinal dystrophy, obesity, polydactyly, mental retardation, hypogonadism, and renal dysfunction. We report a case of 14-year-old obese boy with poor scholastic performances, hypothyroidism, and poor vision diagnosed as BBS.