Bardet-Biedl syndrome: beyond the cilium

Renal Pathology of Ciliopathies

Renal ciliopathies are a group of genetic disorders that affect the function of the primary cilium in the kidney, as well as other organs. Since primary cilia are important for regulation of cell signaling pathways, ciliary dysfunction results in a range of clinical manifestations, including renal failure, cyst formation, and hypertension. We summarize the current understanding of the pathophysiological and pathological features of renal ciliopathies in childhood, including autosomal dominant and recessive polycystic kidney disease, nephronophthisis, and Bardet-Biedl syndrome, as well as skeletal dysplasia associated renal ciliopathies. The genetic basis of these disorders is now well-established in many cases, with mutations in a large number of cilia-related genes such as PKD1, PKD2, BBS, MKS, and NPHP being responsible for the majority of cases. Renal ciliopathies are broadly characterized by development of interstitial fibrosis and formation of multiple renal cysts which gradually enlarge and replace normal renal tissue, with each condition demonstrating subtle differences in the degree, location, and age-related development of cysts and fibrosis. Presentation varies from prenatal diagnosis of congenital multisystem syndromes to an asymptomatic childhood with development of complications in later adulthood and therefore clinicopathological correlation is important, including increasing use of targeted genetic testing or whole genome sequencing, allowing greater understanding of genetic pathophysiological mechanisms.

Shared features in ear and kidney development - implications for oto-renal syndromes

The association between ear and kidney anomalies has long been recognized. However, little is known about the underlying mechanisms. In the last two decades, embryonic development of the inner ear and kidney has been studied extensively. Here, we describe the developmental pathways shared between both organs with particular emphasis on the genes that regulate signalling cross talk and the specification of progenitor cells and specialised cell types. We relate this to the clinical features of oto-renal syndromes and explore links to developmental mechanisms.

BBS genes are involved in accelerated proliferation and early differentiation of BBS-related tissues

Bardet-Biedl syndrome (BBS) is an inherited disorder primarily ciliopathy with pleiotropic multi-systemic phenotypic involvement, including adipose, nerve, retinal, kidney, Etc. Consequently, it is characterized by obesity, cognitive impairment and retinal, kidney and cutaneous abnormalities. Initial studies, including ours have shown that BBS genes play a role in the early developmental stages of adipocytes and β-cells. However, this role in other BBS-related tissues is unknown. We investigated BBS genes involvement in the proliferation and early differentiation of different BBS cell types. The involvement of BBS genes in cellular proliferation were studied in seven in-vitro and transgenic cell models; keratinocytes (hHaCaT) and Ras-transfected keratinocytes (Ras-hHaCaT), neuronal cell lines (hSH-SY5Y and rPC-12), silenced BBS4 neural cell lines (siBbs4 hSH-SY5Y and siBbs4 rPC-12), adipocytes (m3T3L1), and ex-vivo transformed B-cells obtain from BBS4 patients, using molecular and biochemical methodologies. RashHaCaT cells showed an accelerated proliferation rate in parallel to significant reduction in the transcript levels of BBS1, 2, and 4. BBS1, 2, and 4 transcripts linked with hHaCaT cell cycle arrest (G1 phase) using both chemical (CDK4 inhibitor) and serum deprivation methodologies. Adipocyte (m3T3-L1) Bbs1, 2 and 4 transcript levels corresponded to the cell cycle phase (CDK4 inhibitor and serum deprivation). SiBBS4 hSH-SY5Y cells exhibited early cell proliferation and differentiation (wound healing assay) rates. SiBbs4 rPC-12 models exhibited significant proliferation and differentiation rate corresponding to Nestin expression levels. BBS4 patients-transformed B-cells exhibited an accelerated proliferation rate (LPS-induced methodology). In conclusions, the BBS4 gene plays a significant, similar and global role in the cellular proliferation of various BBS related tissues. These results highlight the universal role of the BBS gene in the cell cycle, and further deepen the knowledge of the mechanisms underlying the development of BBS.

Supporting a Tsonga learner living with Bardet-Biedl syndrome, a rare complex disability

Background

Bardet-Biedl syndrome (BBS) is a rare, systemic, hereditary disorder characterised by obesity, polydactyly, visual and auditory impairment, and cognitive disability. Providing quality education in appropriate schools for children who present with such complex chronic conditions is challenging.

Objectives

This study explored the dimensions of psycho-educational support needs for a child with BBS in South Africa to contribute to the improvement of early detection and holistic interventions.

Method

A descriptive in-depth qualitative case study of Gezani, an adolescent Tsonga boy diagnosed with BBS, was undertaken. Semi-structured interviews were conducted with his parents and teachers to ascertain the boy's psycho-educational support needs. Medical reports provided information on the complexities and prognosis of the syndrome. Observations in the classroom corroborated the learner's symptoms and behaviours.

Results

Thematic content analysis revealed the key areas of support needs. Gezani's cognitive disability required a modified, slow-paced curriculum. His visual impairment required mobility orientation training and learning Braille. His emotional needs were supported with psychotherapy to maintain a sense of well-being. Medical monitoring was recommended with interventions for walking and managing his diet and weight. Speech therapy supported his communication skills.

Conclusion

Learners with multiple disabilities require carefully planned, individualised psycho-educational support programmes addressing their unique needs and delays with targeted remedial interventions in appropriate special needs schools.

Contribution

This study informs educators about BBS and provides multi-faceted, holistic support. The Department of Basic Education could bring special schools and national policies in tighter alignment for learners presenting with complex disabilities.

Management of Monogenic and Syndromic Obesity

Similar to the general population, lifestyle interventions focused on nutrition and physical activity form the foundation for treating obesity caused by rare genetic disorders. Additional therapies, including metreleptin and setmelanotide, that target defects within the leptin signaling pathway can effectively synergize with lifestyle efforts to treat monogenic disorders of leptin, leptin receptor, proopiomelanocortin (POMC), and proprotein convertase subtilisin/kexin type 1 (PCSK1) and syndromic conditions, such as the ciliopathies Bardet-Biedl and Alström syndromes, whose pathophysiological mechanisms also converge on the leptin pathway. Investigational treatments for Prader-Willi syndrome target specific defects caused by reduced expression of paternally derived genes within the chromosome 15q region.

Exome sequencing in a Romanian Bardet-Biedl syndrome cohort revealed an overabundance of causal BBS12 variants

Bardet-Biedl syndrome (BBS), is an emblematic ciliopathy hallmarked by pleiotropy, phenotype variability, and extensive genetic heterogeneity. BBS is a rare (~1/140,000 to ~1/160,000 in Europe) autosomal recessive pediatric disorder characterized by retinal degeneration, truncal obesity, polydactyly, cognitive impairment, renal dysfunction, and hypogonadism. Twenty-eight genes involved in ciliary structure or function have been implicated in BBS, and explain the molecular basis for ~75%-80% of individuals. To investigate the mutational spectrum of BBS in Romania, we ascertained a cohort of 24 individuals in 23 families. Following informed consent, we performed proband exome sequencing (ES). We detected 17 different putative disease-causing single nucleotide variants or small insertion-deletions and two pathogenic exon disruptive copy number variants in known BBS genes in 17 pedigrees. The most frequently impacted genes were BBS12 (35%), followed by BBS4, BBS7, and BBS10 (9% each) and BBS1, BBS2, and BBS5 (4% each). Homozygous BBS12 p.Arg355* variants were present in seven pedigrees of both Eastern European and Romani origin. Our data show that although the diagnostic rate of BBS in Romania is likely consistent with other worldwide cohorts (74%), we observed a unique distribution of causal BBS genes, including overrepresentation of BBS12 due to a recurrent nonsense variant, that has implications for regional diagnostics.

Adipose Tissue Hyperplasia and Hypertrophy in Common and Syndromic Obesity-The Case of BBS Obesity

Obesity is a metabolic state generated by the expansion of adipose tissue. Adipose tissue expansion depends on the interplay between hyperplasia and hypertrophy, and is mainly regulated by a complex interaction between genetics and excess energy intake. However, the genetic regulation of adipose tissue expansion is yet to be fully understood. Obesity can be divided into common multifactorial/polygenic obesity and monogenic obesity, non-syndromic and syndromic. Several genes related to obesity were found through studies of monogenic non-syndromic obesity models. However, syndromic obesity, characterized by additional features other than obesity, suggesting a more global role of the mutant genes related to the syndrome and, thus, an additional peripheral influence on the development of obesity, were hardly studied to date in this regard. This review summarizes present knowledge regarding the hyperplasia and hypertrophy of adipocytes in common obesity. Additionally, we highlight the scarce research on syndromic obesity as a model for studying adipocyte hyperplasia and hypertrophy, focusing on Bardet-Biedl syndrome (BBS). BBS obesity involves central and peripheral mechanisms, with molecular and mechanistic alternation in adipocyte hyperplasia and hypertrophy. Thus, we argue that using syndromic obesity models, such as BBS, can further advance our knowledge regarding peripheral adipocyte regulation in obesity.

Retinal Degeneration Animal Models in Bardet-Biedl Syndrome and Related Ciliopathies

Retinal degeneration due to photoreceptor ciliary-related proteins dysfunction accounts for more than 25% of all inherited retinal dystrophies. The cilium, being an evolutionarily conserved and ubiquitous organelle implied in many cellular functions, can be investigated by way of many models from invertebrate models to nonhuman primates, all these models have massively contributed to the pathogenesis understanding of human ciliopathies. Taking the Bardet-Biedl syndrome (BBS) as an emblematic example as well as other related syndromic ciliopathies, the contribution of a wide range of models has enabled to characterize the role of the BBS proteins in the archetypical cilium but also at the level of the connecting cilium of the photoreceptors. There are more than 24 BBS genes encoding for proteins that form different complexes such as the BBSome and the chaperone proteins complex. But how they lead to retinal degeneration remains a matter of debate with the possible accumulation of proteins in the inner segment and/or accumulation of unwanted proteins in the outer segment that cannot return in the inner segment machinery. Many BBS proteins (but not the chaperonins for instance) can be modeled in primitive organisms such as Paramecium, Chlamydomonas reinardtii, Trypanosoma brucei, and Caenorhabditis elegans These models have enabled clarifying the role of a subset of BBS proteins in the primary cilium as well as their relations with other modules such as the intraflagellar transport (IFT) module, the nephronophthisis (NPHP) module, or the Meckel-Gruber syndrome (MKS)/Joubert syndrome (JBTS) module mostly involved with the transition zone of the primary cilia. Assessing the role of the primary cilia structure of the connecting cilium of the photoreceptor cells has been very much studied by way of zebrafish modeling (Danio rerio) as well as by a plethora of mouse models. More recently, large animal models have been described for three BBS genes and one nonhuman primate model in rhesus macaque for BBS7 In completion to animal models, human cell models can now be used notably thanks to gene editing and the use of induced pluripotent stem cells (iPSCs). All these models are not only important for pathogenesis understanding but also very useful for studying therapeutic avenues, their pros and cons, especially for gene replacement therapy as well as pharmacological triggers.

Dental Anomalies in Ciliopathies: Lessons from Patients with BBS2, BBS7, and EVC2 Mutations

Objective: To investigate dental anomalies and the molecular etiology of a patient with Ellis−van Creveld syndrome and two patients with Bardet−Biedl syndrome, two examples of ciliopathies. Patients and Methods: Clinical examination, radiographic evaluation, whole exome sequencing, and Sanger direct sequencing were performed. Results: Patient 1 had Ellis−van Creveld syndrome with delayed dental development or tooth agenesis, and multiple frenula, the feature found only in patients with mutations in ciliary genes. A novel homozygous mutation in EVC2 (c.703G>C; p.Ala235Pro) was identified. Patient 2 had Bardet−Biedl syndrome with a homozygous frameshift mutation (c.389_390delAC; p.Asn130ThrfsTer4) in BBS7. Patient 3 had Bardet−Biedl syndrome and carried a heterozygous mutation (c.389_390delAC; p.Asn130ThrfsTer4) in BBS7 and a homozygous mutation in BBS2 (c.209G>A; p.Ser70Asn). Her clinical findings included global developmental delay, disproportionate short stature, myopia, retinitis pigmentosa, obesity, pyometra with vaginal atresia, bilateral hydronephrosis with ureteropelvic junction obstruction, bilateral genu valgus, post-axial polydactyly feet, and small and thin fingernails and toenails, tooth agenesis, microdontia, taurodontism, and impaired dentin formation. Conclusions: EVC2, BBS2, and BBS7 mutations found in our patients were implicated in malformation syndromes with dental anomalies including tooth agenesis, microdontia, taurodontism, and impaired dentin formation.

Disruption of Dopamine Receptor 1 Localization to Primary Cilia Impairs Signaling in Striatal Neurons

A rod-shaped appendage called a primary cilium projects from the soma of most central neurons in the mammalian brain. The importance of cilia within the nervous system is highlighted by the fact that human syndromes linked to primary cilia dysfunction, collectively termed ciliopathies, are associated with numerous neuropathologies, including hyperphagia-induced obesity, neuropsychiatric disorders, and learning and memory deficits. Neuronal cilia are enriched with signaling molecules, including specific G-protein-coupled receptors (GPCRs) and their downstream effectors, suggesting that they act as sensory organelles that respond to neuromodulators in the extracellular space. We previously showed that GPCR ciliary localization is disrupted in neurons from mouse models of the ciliopathy Bardet-Biedl syndrome (BBS). Based on this finding, we hypothesized that mislocalization of ciliary GPCRs may impact receptor signaling and contribute to the BBS phenotypes. Here, we show that disrupting localization of the ciliary GPCR dopamine receptor 1 (D1) in male and female mice, either by loss of a BBS protein or loss of the cilium itself, specifically in D1-expressing neurons, results in obesity. Interestingly, the weight gain is associated with reduced locomotor activity, rather than increased food intake. Moreover, the loss of a BBS protein or cilia on D1-expressing neurons leads to a reduction in D1-mediated signaling. Together, these results indicate that cilia impact D1 activity in the nervous system and underscore the importance of neuronal cilia for proper GPCR signaling.SIGNIFICANCE STATEMENT Most mammalian neurons possess solitary appendages called primary cilia. These rod-shaped structures are enriched with signaling proteins, such as G-protein-coupled receptors (GPCRs), suggesting that they respond to neuromodulators. This study examines the consequences of disrupting ciliary localization of the GPCR dopamine receptor 1 (D1) in D1-expressing neurons. Remarkably, mice that have either an abnormal accumulation of D1 in cilia or a loss of D1 ciliary localization become obese. In both cases, the obesity is associated with lower locomotor activity rather than overeating. As D1 activation increases locomotor activity, these results are consistent with a reduction in D1 signaling. Indeed, we found that D1-mediated signaling is reduced in brain slices from both mouse models. Thus, cilia impact D1 signaling in the brain.

Atypical phenotype of a patient with Bardet-Biedl syndrome type 4

Background

Bardet–Biedl syndrome (BBS) is a multisystemic disorder characterized by rod–cone dystrophy, truncal obesity, postaxial polydactyly, cognitive impairment, male hypogonadotropic hypogonadism, complex female genitourinary malformations, and renal abnormalities. There is a large clinical and also genetic heterogeneity in BBS. Here, we report a patient with polydactyly, hyperechogenic kidneys increased in size with normal corticomedullary differentiation, anal imperforation, and malformation of genitals with presence of a genital tubercle with ventral urethral meatus associated with two unfused lateral genital swelling and absent urethral folds, in the context of 46, XY karyotype.

Methods

Karyotype and solo exome sequencing were performed to look for a genetic etiology for the features described in our patient.

Results

We identified a homozygous in‐frame deletion of exons 4 to 6 in the BBS4 gene (NM‐033028 (BBS4‐i001): c.[(157‐?)_(405 +?)del] p.(Ala53‐Trp135del), which is classified as pathogenic variant. This analysis allowed the molecular diagnosis of BBS type 4 in this patient.

Conclusion

Complex genital malformations are only reported in female BBS6 patients yet, and genital abnormalities and anal imperforation are not reported in male BBS4 patients to date. We discuss the possible hypotheses for this phenotype, including the phenotypic overlap between ciliopathies.

[Genetic screening is essential in polycystic kidney disease: It is never too late!]

In France, numerous patients suffered from chronic kidney disease on polycystic kidney disorder. If PKD1 and PKD2 inactivating mutations are the most prevalent, several other genetic polycystic kidney diseases are responsible for similar kidney features and may be associated with severe extrarenal phenotypes. Genetic analysis in front of a polycystic disorder is not systematic, but is essential to assess the genetic diagnosis, discuss the intensity of treatment (vaptan) and precise the prognostic and the transmission of the phenotype. We detailed the case of a patient with end stage renal disease due to a polycystic kidney disease. Genetic analysis at 70 year of age revealed an oral-facial-digital syndrome type 1. The diagnosis had an important impact in the familial history and to attach the extrarenal phenotype to the syndrome. Our case illustrates that, in front of a polycystic kidney disease (even in aged patients with end stage renal disease) genetic screening is essential, for the propositus and their family and to take care of the extrarenal manifestations.

Retinal ciliopathies through the lens of Bardet-Biedl Syndrome: Past, present and future

The primary cilium is a highly specialized and evolutionary conserved organelle in eukaryotes that plays a significant role in cell signaling and trafficking. Over the past few decades tremendous progress has been made in understanding the physiology of cilia and the underlying pathomechanisms of various ciliopathies. Syndromic ciliopathies consist of a group of disorders caused by ciliary dysfunction or abnormal ciliogenesis. These disorders have multiorgan involvement in addition to retinal degeneration underscoring the ubiquitous distribution of primary cilia in different cell types. Genotype-phenotype correlation is often challenging due to the allelic heterogeneity and pleiotropy of these disorders. In this review, we discuss the clinical and genetic features of syndromic ciliopathies with a focus on Bardet-Biedl syndrome (BBS) as a representative disorder. We discuss the structure and function of primary cilia and their role in retinal photoreceptors. We describe the progress made thus far in understanding the functional and genetic characterization including expression quantitative trait locus (eQTL) analysis of BBS genes. In the future directions section, we discuss the emerging technologies, such as gene therapy, as well as anticipated challenges and their implications in therapeutic development for ciliopathies.

The Role of Centrosome Distal Appendage Proteins (DAPs) in Nephronophthisis and Ciliogenesis

The primary cilium is found in most mammalian cells and plays a functional role in tissue homeostasis and organ development by modulating key signaling pathways. Ciliopathies are a group of genetically heterogeneous disorders resulting from defects in cilia development and function. Patients with ciliopathic disorders exhibit a range of phenotypes that include nephronophthisis (NPHP), a progressive tubulointerstitial kidney disease that commonly results in end-stage renal disease (ESRD). In recent years, distal appendages (DAPs), which radially project from the distal end of the mother centriole, have been shown to play a vital role in primary ciliary vesicle docking and the initiation of ciliogenesis. Mutations in the genes encoding these proteins can result in either a complete loss of the primary cilium, abnormal ciliary formation, or defective ciliary signaling. DAPs deficiency in humans or mice commonly results in NPHP. In this review, we outline recent advances in our understanding of the molecular functions of DAPs and how they participate in nephronophthisis development.

Network analysis reveals rare disease signatures across multiple levels of biological organization

Rare genetic diseases are typically caused by a single gene defect. Despite this clear causal relationship between genotype and phenotype, identifying the pathobiological mechanisms at various levels of biological organization remains a practical and conceptual challenge. Here, we introduce a network approach for evaluating the impact of rare gene defects across biological scales. We construct a multiplex network consisting of over 20 million gene relationships that are organized into 46 network layers spanning six major biological scales between genotype and phenotype. A comprehensive analysis of 3,771 rare diseases reveals distinct phenotypic modules within individual layers. These modules can be exploited to mechanistically dissect the impact of gene defects and accurately predict rare disease gene candidates. Our results show that the disease module formalism can be applied to rare diseases and generalized beyond physical interaction networks. These findings open up new venues to apply network-based tools for cross-scale data integration.

Correction of cilia structure and function alleviates multi-organ pathology in Bardet-Biedl syndrome mice

Bardet–Biedl syndrome (BBS) is a pleiotropic autosomal recessive ciliopathy affecting multiple organs. The development of potential disease-modifying therapy for BBS will require concurrent targeting of multi-systemic manifestations. Here, we show for the first time that monosialodihexosylganglioside accumulates in Bbs2^−/− cilia, indicating impairment of glycosphingolipid (GSL) metabolism in BBS. Consequently, we tested whether BBS pathology in Bbs2^−/− mice can be reversed by targeting the underlying ciliary defect via reduction of GSL metabolism. Inhibition of GSL synthesis with the glucosylceramide synthase inhibitor Genz-667161 decreases the obesity, liver disease, retinal degeneration and olfaction defect in Bbs2^−/− mice. These effects are secondary to preservation of ciliary structure and signaling, and stimulation of cellular differentiation. In conclusion, reduction of GSL metabolism resolves the multi-organ pathology of Bbs2^−/− mice by directly preserving ciliary structure and function towards a normal phenotype. Since this approach does not rely on the correction of the underlying genetic mutation, it might translate successfully as a treatment for other ciliopathies.

Apparent but unconfirmed digenism in an Iranian consanguineous family with syndromic Retinal Disease

BACKGROUND

Bardet-Biedl syndrome is an autosomal recessive disease characterized by rod-cone dystrophy, postaxial polydactyly, kidney defects, obesity, mental retardation and hypogonadism. Here, we report different genotypes in two Bardet-Biedl syndrome affected sisters with a different clinical phenotype regarding severity.

MATERIALS AND METHODS

The proband of the family was examined by Next Generation Sequencing (NGS) using clinical exome and filtering by syndromic and non-syndromic genes associated with retinal dystrophies.

RESULTS

Targeted NGS revealed two novel variants in the MKKS and CEP290 genes in homozygosis state in the proband. Segregation analysis revealed the presence of the same MKKS homozygous variant in her younger affected sister but not the CEP290 variant. Both sisters presented different clinical manifestation, at different ages, with a more severe renal and retinal defect in the case of the sister carrying mutations in both genes. Another unaffected sister showed only homozygosity for the CEP290 variant, thus supporting the non-pathogenic role of this mutation in BBS phenotype.

CONCLUSIONS

In this study, NGS proved to be a powerful and efficient sequencing method to identify causal variants in different genes. However, it remarks the importance of the segregation analysis and clinical information to establish the pathogenicity of new variants. The two affected sisters present different genotypes and clinical manifestation, suggesting that the novel CEP290 variant could be acting as a modifier, making the phenotype more severe in the sister homozygote for MKKS and CEP290 genes. On the other hand, the difference in the age of both sisters highlight the important role of monitoring disease progression also to confirm the modifier role of genetic variants.

Alström syndrome: an ultra-rare monogenic disorder as a model for insulin resistance, type 2 diabetes mellitus and obesity

BACKGROUND

Alström syndrome (ALMS) is a monogenic ultra-rare disorder with a prevalence of one per million inhabitants caused by pathogenic variants of ALMS1 gene. ALMS1 is located on chromosome 2p13, spans 23 exons and encodes a predicted 461.2-kDa protein of 4169 amino acids. The infantile cone-rod dystrophy with nystagmus and severe visual impairment is the earliest and most consistent clinical manifestation of ALMS. In addition, infantile transient cardiomyopathy, early childhood obesity with hyperphagia, deafness, insulin resistance (IR), type 2 diabetes mellitus (T2DM), systemic fibrosis and progressive renal or liver dysfunction are common findings. ALMS1 encodes a large ubiquitously expressed protein that is associated with the centrosome and the basal body of primary cilium.

CURRENT RESEARCH

The localisation of ALMS1 to the ciliary basal body suggests its contribution to ciliogenesis and/or normal ciliary function, or centriolar stability. ALMS1 regulate glucose transport through the actin cytoskeleton, which plays an important role in insulin-stimulated GLUT4 transport. Both extreme IR and β-cell failure are the two determinant factors responsible for the development of glucose metabolism alterations in ALMS.

TREATMENT

Currently, there is no known cure for ALMS other than managing the underlying systemic diseases. When possible, individuals with ALMS and families should be referred to a centre of expertise and followed by a multidisciplinary team. Lifestyle modification, aerobic exercise and dietary induced weight loss are highly recommended as primary treatment for ALMS patients with T2DM and obesity.

CONCLUSION

Managing a rare disease requires not only medical care but also a support network including patient associations.

A Unique Manifestation of Bardet-Biedl Syndrome with Otolaryngologic Symptoms and Bronchopneumonia in a One-year-old Girl

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive genetic disorder. It is a congenital ciliopathy that has primary and secondary characteristics. Primary clinical features include rod-cone dystrophy, polydactyly, central obesity, genital abnormalities and mental retardation often presenting as learning difficulties. Secondary clinical features include developmental delay, speech deficit, brachydactyly/syndactyly, dental defects, ataxia, olfactory deficit, diabetes mellitus (DM) and congenital heart disease. BBS patients are friendly with a happy predisposition. Proper management, and regular examinations should be done in order to maintain healthy organ function and to avoid an early death. Renal failure is the most common cause of mortality in BBS patients.This case report illustrates the evaluation of a child with BBS, as well as the unique association of otolaryngologic symptoms and bronchopneumonia with it.

Meta-analysis of genotype-phenotype associations in Bardet-Biedl syndrome uncovers differences among causative genes

Bardet-Biedl syndrome (BBS) is a recessive genetic disease causing multiple organ anomalies. Most patients carry mutations in genes encoding for the subunits of the BBSome, an octameric ciliary transport complex, or accessory proteins involved in the BBSome assembly or function. BBS proteins have been extensively studied using in vitro, cellular, and animal models. However, the molecular functions of particular BBS proteins and the etiology of the BBS symptoms are still largely elusive. In this study, we applied a meta-analysis approach to study the genotype-phenotype association in humans using our database of all reported BBS patients. The analysis revealed that the identity of the causative gene and the character of the mutation partially predict the clinical outcome of the disease. Besides their potential use for clinical prognosis, our analysis revealed functional differences of particular BBS genes in humans. Core BBSome subunits BBS2, BBS7, and BBS9 manifest as more critical for the function and development of kidneys than peripheral subunits BBS1, BBS4, and BBS8/TTC8, suggesting that incomplete BBSome retains residual function at least in the kidney.

Primary cilia: biosensors of the male reproductive tract

BACKGROUND

The primary cilium is a microtubule-based organelle that extends transiently from the apical cell surface to act as a sensory antenna. Initially viewed as a cellular appendage of obscure significance, the primary cilium is now acknowledged as a key coordinator of signaling pathways during development and in tissue homeostasis.

OBJECTIVES

The aim of this review was to present the structure and function of this overlooked organelle,with an emphasis on its epididymal context and contribution to male infertility issues.

MATERIALS AND METHODS

A systematic review has been performed in order to include main references relevant to the aforementioned topic.

RESULTS

Increasing evidence demonstrates that primary cilia dysfunctions are associated with impaired male reproductive system development and male infertility issues.

DISCUSSION

While a large amount of data exists regarding the role of primary cilia in most organs and tissues, few studies investigated the contribution of these organelles to male reproductive tract development and homeostasis.

CONCLUSION

Functional studies of primary cilia constitute an emergent and exciting new area in reproductive biology research.

A pathogenic homozygous variant of the BBS10 gene in a patient with Bardet Biedl syndrome

The Bardet-Biedl syndrome is an autosomal recessive hereditary disorder with vast locus heterogeneity that belongs to the so-called ciliopathies, whose proteins are localized in the primary cilia and present functional deficiency. The multisystemic features of the disease include ocular, renal, cognitive, skeletal, as well as gonadal involvement and obesity, among others, with high inter- and intrafamilial variability. We describe the clinical case of an adolescent male patient with Bardet-Biedl syndrome, including the approach, the results from a 22-gene sequencing panel, and the analysis of updated scientific literature. We collected the clinical data of the patient and, after obtaining the informed consent, we conducted a multigenic sequencing panel oriented to known implicated genes. The patient was born to consanguineous parents and was the first affected member of the family. He presented with postaxial polydactyly, obesity, micropenis, retinitis pigmentosa, and learning disability. The multigenic panel allowed the identification of the homozygous pathogenic variant c.39_46del in the BBS10 gene and in other BBS genes variants associated with obesity. As the Bardet-Biedl syndrome is a rare disease, it is challenging to interpret its pleiotropism and gene/allelic heterogeneity. Its confirmation by molecular tests allows an adequate approach, follow-up, and genetic counseling of the patient and the family.

BBS9 gene in nonsyndromic craniosynostosis: Role of the primary cilium in the aberrant ossification of the suture osteogenic niche

Nonsyndromic craniosynostosis (NCS) is the premature ossification of skull sutures, without associated clinical features. Mutations in several genes account for a small number of NCS patients; thus, the molecular etiopathogenesis of NCS remains largely unclear. Our study aimed at characterizing the molecular signaling implicated in the aberrant ossification of sutures in NCS patients. Comparative gene expression profiling of NCS patient sutures identified a fused suture-specific signature, including 17 genes involved in primary cilium signaling and assembly. Cells from fused sutures displayed a reduced potential to form primary cilia compared to cells from control patent sutures of the same patient. We identified specific upregulated splice variants of the Bardet Biedl syndrome-associated gene 9 (BBS9), which encodes a structural component of the ciliary BBSome complex. BBS9 expression increased during in vitro osteogenic differentiation of suture-derived mesenchymal cells of NCS patients. Also, Bbs9 expression increased during in vivo ossification of rat sutures. BBS9 functional knockdown affected the expression of primary cilia on patient suture cells and their osteogenic potential. Computational modeling of the upregulated protein isoforms (observed in patients) predicted that their binding affinity within the BBSome may be affected, providing a possible explanation for the aberrant suture ossification in NCS.

Pharmacogenetics of post-transplant diabetes mellitus in children with renal transplantation treated with tacrolimus

BACKGROUND

Post-transplant diabetes mellitus (PTDM) is a major complication of immunosuppressive therapy, with many risk factors reported in adults with renal transplantation. The objective of this study was to investigate potential non-genetic and genetic risk factors of PTDM in children with renal transplantation treated with tacrolimus.

METHODS

A national database was screened for patients developing PTDM within 4 years following tacrolimus introduction. PTDM was defined as glucose disorder requiring anti-diabetic treatment. PTDM patients were matched to "non-PTDM" control transplanted children according to age, gender, and duration of post-transplant follow-up. Patients were genotyped for six selected genetic variants in POR*28 (rs1057868), PPARa (rs4253728), CYP3A5 (rs776746), VDR (rs2228570 and rs731236), and ABCB1 (rs1045642) genes, implicated in glucose homeostasis and tacrolimus disposition.

RESULTS

Among the 98 children with renal transplantation enrolled in this multicentre study, 18 developed PTDM. None of the clinical and biological parameters was significant between PTDM and control patients. Homozygous carriers of POR*28 or wild-type ABCB1 (rs1045642) gene variants were more frequent in PTDM than in control patients with differences close to significance (p = 0.114 and p = 0.066 respectively). A genetic score based on these variants demonstrated that POR*28/*28 and ABCB1 CC or CT genotype carriers were at a significantly higher risk of developing PTDM after renal transplantation.

CONCLUSION

Identification of PTDM risk factors should allow clinicians to allocate the best immunosuppressant for each patient with renal transplantation, and improve care for patients who are at a higher risk.

The Endocrine and Metabolic Characteristics of a Large Bardet-Biedl Syndrome Clinic Population

CONTEXT

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive disorder in which previous reports have described obesity and a metabolic syndrome.

OBJECTIVE

We describe the endocrine and metabolic characteristics of a large BBS population compared with matched control subjects.

DESIGN

We performed a case-control study.

SETTING

This study was performed at a hospital clinic.

PATIENTS

Study patients had a clinical or genetic diagnosis of BBS.

MAIN OUTCOME MEASUREMENTS

Our study determined the prevalence of a metabolic syndrome in our cohort.

RESULTS

A total of 152 subjects were studied. Eighty-four (55.3%) were male. Mean (± standard deviation) age was 33.2 ± 1.0 years. Compared with age-, sex-, and body mass index-matched control subjects, fasting glucose and insulin levels were significantly higher in subjects with BBS (glucose: BBS, 5.2 ± 1.2 mmol/L vs control, 4.9 ± 0.9 mmol/L, P = 0.04; insulin: BBS, 24.2 ± 17.0 pmol/L vs control, 14.2 ± 14.8 pmol/L, P < 0.001). Serum triglycerides were significantly higher in subjects with BBS (2.0 ± 1.2 mmol/L) compared with control subjects (1.3 ± 0.8 mmol/L; P < 0.001), but total cholesterol, high-density lipoprotein, and low-density lipoprotein were similar in both groups. Systolic blood pressure was higher in the BBS group (BBS, 135 ± 18 mm Hg vs control subjects, 129 ± 16 mm Hg; P = 0.02). Alanine transaminase was raised in 34 (26.8%) subjects with BBS, compared with five (8.9%) control subjects (P = 0.01). The rate of metabolic syndrome, determined using International Diabetes Federation criteria, was significantly higher in the BBS group (54.3%) compared with control subjects (26% P < 0.001). Twenty-six (19.5%) of male subjects with BBS were hypogonadal (serum testosterone, 9.9 ± 5.3 mmol/L), but significant pituitary abnormalities were uncommon. Subclinical hypothyroidism was present in 24 of 125 (19.4%) patients with BBS, compared with 3 of 65 (4.6%) control subjects (P = 0.01).

CONCLUSIONS

Insulin resistance and the metabolic syndrome are increased in adult patients with BBS compared with matched control subjects. Increased subclinical hypothyroidism in the BBS cohort needs further investigation.

Managing Bardet-Biedl Syndrome-Now and in the Future

Bardet-Biedl syndrome is a rare autosomal recessive multisystem disorder caused by defects in genes encoding for proteins that localize to the primary cilium/basal body complex. Twenty-one disease-causing genes have been identified to date. It is one of the most well-studied conditions in the family of diseases caused by defective cilia collectively known as ciliopathies. In this review, we provide an update on diagnostic developments, clinical features, and progress in the management of Bardet-Biedl syndrome. Advances in diagnostic technologies including exome and whole genome sequencing are expanding the spectrum of patients who are diagnosed with Bardet-Biedl syndrome and increasing the number of cases with diagnostic uncertainty. As a result of the diagnostic developments, a small number of patients with only one or two clinical features of Bardet-Biedl syndrome are being diagnosed. Our understanding of the syndrome-associated renal disease has evolved and is reviewed here. Novel interventions are developing at a rapid pace and are explored in this review including genetic therapeutics such as gene therapy, exon skipping therapy, nonsense suppression therapy, and gene editing. Other non-genetic therapies such as gene repurposing, targeted therapies, and non-pharmacological interventions are also discussed.

Mutations in the Katnb1 gene cause left-right asymmetry and heart defects

BACKGROUND

The microtubule-severing protein complex katanin is composed two subunits, the ATPase subunit, KATNA1, and the noncatalytic regulatory subunit, KATNB1. Recently, the Katnb1 gene has been linked to infertility, regulation of centriole and cilia formation in fish and mammals, as well as neocortical brain development. KATNB1 protein is expressed in germ cells in humans and mouse, mitotic/meiotic spindles and cilia, although the full expression pattern of the Katnb1 gene has not been described.

RESULTS

Using a knockin-knockout mouse model of Katnb1 dysfunction we demonstrate that Katnb1 is ubiquitously expressed during embryonic development, although a stronger expression is seen in the crown cells of the gastrulation organizer, the murine node. Furthermore, null and hypomorphic Katnb1 gene mutations show a novel correlation between Katnb1 dysregulation and the development of impaired left-right signaling, including cardiac malformations.

CONCLUSIONS

Katanin function is a critical regulator of heart development in mice. These findings are potentially relevant to human cardiac development. Developmental Dynamics 246:1027-1035, 2017. © 2017 Wiley Periodicals, Inc.

Hedgehog signalling in myeloid cells impacts on body weight, adipose tissue inflammation and glucose metabolism

AIMS/HYPOTHESIS

Recently, hedgehog (Hh) was identified as a crucial player in adipose tissue development and energy expenditure. Therefore, we tested whether Hh ligands are regulated in obesity. Further, we aimed at identifying potential target cells of Hh signalling and studied the functional impact of Hh signalling on adipose tissue inflammation and glucose metabolism.

METHODS

Hh ligands and receptors were analysed in adipose tissue or serum from lean and obese mice as well as in humans. To study the impact on adipose tissue inflammation and glucose metabolism, Hh signalling was specifically blocked in myeloid cells using a conditional knockout approach (Lys-Smo ^-/-).

RESULTS

Desert Hh (DHH) and Indian Hh (IHH) are local Hh ligands, whereas Sonic Hh is not expressed in adipose tissue from mice or humans. In mice, obesity leads to a preferential upregulation of Hh ligands (Dhh) and signalling components (Ptch1, Smo and Gli1) in subcutaneous adipose tissue. Further, adipose tissue macrophages are Hh target cells owing to the expression of Hh receptors, such as Patched1 and 2. Conditional knockout of Smo (which encodes Smoothened, a mandatory Hh signalling component) in myeloid cells increases body weight and adipose tissue inflammation and attenuates glucose tolerance, suggesting an anti-inflammatory effect of Hh signalling. In humans, adipose tissue expression of DHH and serum IHH decrease with obesity and type 2 diabetes, which might be explained by the intake of metformin. Interestingly, metformin reduced Dhh and Ihh expression in mouse adipose tissue explants.

CONCLUSIONS/INTERPRETATION

Hh signalling in myeloid cells affects adipose tissue inflammation and glucose metabolism and may be a potential target to treat type 2 diabetes.

What we can learn from a tadpole about ciliopathies and airway diseases: Using systems biology in Xenopus to study cilia and mucociliary epithelia

Over the past years, the Xenopus embryo has emerged as an incredibly useful model organism for studying the formation and function of cilia and ciliated epithelia in vivo. This has led to a variety of findings elucidating the molecular mechanisms of ciliated cell specification, basal body biogenesis, cilia assembly, and ciliary motility. These findings also revealed the deep functional conservation of signaling, transcriptional, post-transcriptional, and protein networks employed in the formation and function of vertebrate ciliated cells. Therefore, Xenopus research can contribute crucial insights not only into developmental and cell biology, but also into the molecular mechanisms underlying cilia related diseases (ciliopathies) as well as diseases affecting the ciliated epithelium of the respiratory tract in humans (e.g., chronic lung diseases). Additionally, systems biology approaches including transcriptomics, genomics, and proteomics have been rapidly adapted for use in Xenopus, and broaden the applications for current and future translational biomedical research. This review aims to present the advantages of using Xenopus for cilia research, highlight some of the evolutionarily conserved key concepts and mechanisms of ciliated cell biology that were elucidated using the Xenopus model, and describe the potential for Xenopus research to address unresolved questions regarding the molecular mechanisms of ciliopathies and airway diseases.

Renal phenotype in Bardet-Biedl syndrome: a combined defect of urinary concentration and dilution is associated with defective urinary AQP2 and UMOD excretion

The renal phenotype in Bardet-Biedl syndrome (BBS) is highly variable. The present study describes renal findings in 41 BBS patients and analyzes the pathogenesis of hyposthenuria, the most common renal dysfunction. Five of 41 patients (12%) showed an estimated glomerular filtration rate < 60 ml·min-1·1.73 m-2 Urine protein and urine albumin-to-creatinine ratio were over 200 and 30 mg/g in 9/24 and 7/23 patients, respectively. Four of 41 patients showed no renal anomalies on ultrasound. Twenty of 34 patients had hyposthenuria in the absence of renal insufficiency. In all 8 of the hyposthenuric patients studied, dDAVP failed to elevate urine osmolality (Uosm), suggesting a nephrogenic origin. Interestingly, water loading (WL) did not result in a significant reduction of Uosm, indicating combined concentrating and diluting defects. dDAVP infusion induced a significant increase of plasma Factor VIII and von Willebrand Factor levels, supporting normal function of the type 2 vasopressin receptor at least in endothelial cells. While urinary aquaporin 2 (u-AQP2) abundance was not different between patients and controls at baseline, the dDAVP-induced increased u-AQP2 and the WL-induced reduction of u-AQP2 were blunted in patients with a combined concentrating and diluting defect, suggesting a potential role of AQP2 in the defective regulation of water absorption. Urine Uromodulin excretion was reduced in all hyposthenuric patients, suggesting a thick ascending limb defect. Interestingly, renal Na, Cl, Ca, but not K handling was impaired after acute WL but not at basal. In summary, BBS patients show combined urinary concentration and dilution defects; a thick ascending limb and collecting duct tubulopathy may underlie impaired water handling.

[Algorithm for the molecular analysis of Bardet-Biedl syndrome in Spain]

BACKGROUND AND OBJECTIVE

Bardet-Biedl syndrome (BBS) is a multisystemic genetic disorder, which is not widespread among the Caucasian population, characterized by a highly variable phenotype and great genetic heterogeneity. BBS belongs to a group of diseases called ciliopathies, caused by defects in the structure and/or function of cilia. Due to the diagnostic complexity of the syndrome, the objective of this study was to analyse our whole group of patients in order to create an algorithm to facilitate the routine molecular diagnosis of BBS. We also calculated several epidemiological parameters in our cohort.

PATIENTS AND METHOD

We analysed 116 BBS patients belonging to 89 families from the whole Spanish geography. All probands fulfilled diagnosis criteria established for BBS. For this, we used: genotyping microarray, direct sequencing and homozygosis mapping (in consanguineous families).

RESULTS

By means of the different approaches, it was possible to diagnose 47% of families (21% by genotyping microarray, 18% by direct sequencing of predominant BBS genes, and 8% by homozygosis mapping). With regard to epidemiological data, a prevalence value of 1:407,000 was obtained for BBS in Spain, and a sex ratio of 1.4:1 (men:women).

CONCLUSIONS

The proposed algorithm, based on the analysis of predominant BBS genes combined with homozygosis mapping, allowed us to confirm the molecular diagnosis in a significant percentage of families with clinically suspected BBS. This diagnostic algorithm will be useful for the improvement of the efficiency of molecular analysis in BBS.

New-onset diabetes after kidney transplant in children

The development of new-onset diabetes after kidney transplantation (NODAT) is associated with reduced graft function, increased cardiovascular morbidity and lower patient survival among adult recipients. In the pediatric population, however, the few studies examining NODAT have yielded inconsistent results. Therefore, the true incidence of NODAT in the pediatric population has been difficult to establish. The identification of children and adolescents at risk for NODAT requires appropriate screening questions and tests pre- and post-kidney transplant. Several risk factors have been implicated in the pathogenesis of NODAT and post-transplant glucose intolerance, including African American race, obesity, family history of diabetes and the type of immunosuppressant regimen. Moreover, uremia per se results in a state of insulin resistance that increases the risk of developing diabetes post-transplant. When an individual becomes glucose intolerant, early lifestyle modification and antihyperglycemic measures with tailoring of the immunosuppressant regimen should be implemented to prevent the development of NODAT. For the child or adolescent with NODAT, antihyperglycemic therapy should be prescribed in order to achieve optimal glycemic control, ultimately reducing complications and improving overall allograft and patient survival. In this article, we review the risk factors, screening methods, diagnosis, management and outcome of children and adolescents with NODAT and post-kidney transplant glucose intolerance.

Locus heterogeneity disease genes encode proteins with high interconnectivity in the human protein interaction network

Mutations in genes potentially lead to a number of genetic diseases with differing severity. These disease genes have been the focus of research in recent years showing that the disease gene population as a whole is not homogeneous, and can be categorized according to their interactions. Locus heterogeneity describes a single disorder caused by mutations in different genes each acting individually to cause the same disease. Using datasets of experimentally derived human disease genes and protein interactions, we created a protein interaction network to investigate the relationships between the products of genes associated with a disease displaying locus heterogeneity, and use network parameters to suggest properties that distinguish these disease genes from the overall disease gene population. Through the manual curation of known causative genes of 100 diseases displaying locus heterogeneity and 397 single-gene Mendelian disorders, we use network parameters to show that our locus heterogeneity network displays distinct properties from the global disease network and a Mendelian network. Using the global human proteome, through random simulation of the network we show that heterogeneous genes display significant interconnectivity. Further topological analysis of this network revealed clustering of locus heterogeneity genes that cause identical disorders, indicating that these disease genes are involved in similar biological processes. We then use this information to suggest additional genes that may contribute to diseases with locus heterogeneity.

Structural basis for membrane targeting of the BBSome by ARL6

The BBSome is a coat-like ciliary trafficking complex composed of proteins mutated in Bardet-Biedl syndrome (BBS). A critical step in BBSome-mediated sorting is recruitment of the BBSome to membranes by the GTP-bound Arf-like GTPase ARL6. We have determined crystal structures of Chlamydomonas reinhardtii ARL6-GDP, ARL6-GTP and the ARL6-GTP-BBS1 complex. The structures demonstrate how ARL6-GTP binds the BBS1 β-propeller at blades 1 and 7 and explain why GTP- but not GDP-bound ARL6 can recruit the BBSome to membranes. Single point mutations in the ARL6-GTP-BBS1 interface abolish the interaction of ARL6 with the BBSome and prevent the import of BBSomes into cilia. Furthermore, we show that BBS1 with the M390R mutation, responsible for 30% of all reported BBS disease cases, fails to interact with ARL6-GTP, thus providing a molecular rationale for patient pathologies.

BBS4 directly affects proliferation and differentiation of adipocytes

BBS4 is one of several proteins whose defects cause Bardet-Biedl syndrome (BBS), a multi-systemic disorder, manifesting with marked obesity. BBS4 polymorphisms have been associated with common non-syndromic morbid obesity. BBS4 obesity molecular mechanisms, and the role of the BBS4 gene in adipocyte differentiation and function are not entirely known. We now show that Bbs4 plays a direct and essential role in proliferation and adipogenesis: silencing of Bbs4 in 3T3F442A preadipocytes induced accelerated cell division and aberrant differentiation, evident through morphologic studies (light, scanning and transmission electron microscopy), metabolic analyses (fat accumulation, fatty acid profile and lipolysis) and adipogenic markers transcripts (Cebpα, Pparγ, aP2, ADRP, Perilipin). Throughout adipogenesis and when challenged with fat load, Bbs4 silenced cells accumulate significantly more triglycerides than control adipocytes, albeit in smaller (yet greater in number) droplets containing modified fatty acid profiles. Thus, greater fat accumulation in the silenced cells is a consequence of both a higher rate of adipocyte proliferation and of aberrant differentiation leading to augmented aberrant accumulation of fat per cell. Our findings suggest that the BBS obesity might be partly due to a direct role of BBS4 in physiological and pathophysiological mechanisms that underlie adipose tissue formation relevant to obesity.

A case of Bardet-Biedl syndrome complicated with intracranial hypertension in a Japanese child

Bardet-Biedl syndrome (BBS) is a rare heterogeneous autosomal recessive disorder characterized by rod-cone dystrophy, postaxial polydactyly, truncal obesity, hypogonadism, learning disability, and renal anomaly that are caused by ciliary dysfunction. 16 genes have been associated with the BBS phenotype. Although recent pathophysiological studies using animal models have shown that ciliary dysfunction may induce hydrocephalus, there have been no reports of BBS with intracranial hypertension. We here describe a 9-year-old Japanese girl who was diagnosed as having BBS and later received renal transplantation due to chronic renal failure. She also exhibited intracranial hypertension, including papilledema and increased intrathecal pressure (260-300 mmH2O), but her brain magnetic resonance imaging was normal. No genetic abnormalities were detected by DNA chip analysis or exome sequencing. Her papilledema improved following administration of acetazolamide. This is the first report of a case of BBS complicated with intracranial hypertension and its treatment.

Genetic strategies to understand physiological pathways regulating body weight

Body weight is a highly heritable trait across species. In humans, genetic variation plays a major role in determining the inter-individual differences in susceptibility or resistance to environmental factors which influence energy intake and expenditure. In this review, I discuss how genetic studies have contributed to our understanding of the central pathways that govern energy homeostasis. The study of individuals harboring highly penetrant genetic variants that disrupt the leptin–melanocortin pathway has informed our understanding of the physiological pathways involved in mammalian energy homeostasis.

Identification of conserved, centrosome-targeting ASH domains in TRAPPII complex subunits and TRAPPC8

BACKGROUND

Assembly of primary cilia relies on vesicular trafficking towards the cilium base and intraflagellar transport (IFT) between the base and distal tip of the cilium. Recent studies have identified several key regulators of these processes, including Rab GTPases such as Rab8 and Rab11, the Rab8 guanine nucleotide exchange factor Rabin8, and the transport protein particle (TRAPP) components TRAPPC3, -C9, and -C10, which physically interact with each other and function together with Bardet Biedl syndrome (BBS) proteins in ciliary membrane biogenesis. However, despite recent advances, the exact molecular mechanisms by which these proteins interact and target to the basal body to promote ciliogenesis are not fully understood.

RESULTS

We surveyed the human proteome for novel ASPM, SPD-2, Hydin (ASH) domain-containing proteins. We identified the TRAPP complex subunits TRAPPC8, -9, -10, -11, and -13 as novel ASH domain-containing proteins. In addition to a C-terminal ASH domain region, we predict that the N-terminus of TRAPPC8, -9, -10, and -11, as well as their yeast counterparts, consists of an α-solenoid bearing stretches of multiple tetratricopeptide (TPR) repeats. Immunofluorescence microscopy analysis of cultured mammalian cells revealed that exogenously expressed ASH domains, as well as endogenous TRAPPC8, localize to the centrosome/basal body. Further, depletion of TRAPPC8 impaired ciliogenesis and GFP-Rabin8 centrosome targeting.

CONCLUSIONS

Our results suggest that ASH domains confer targeting to the centrosome and cilia, and that TRAPPC8 has cilia-related functions. Further, we propose that the yeast TRAPPII complex and its mammalian counterpart are evolutionarily related to the bacterial periplasmic trafficking chaperone PapD of the usher pili assembly machinery.

Closing the Gap: Genetic and Genomic Continuum from Syndromic to Nonsyndromic Craniosynostoses

Craniosynostosis, a condition that includes the premature fusion of one or multiple cranial sutures, is a relatively common birth defect in humans and the second most common craniofacial anomaly after orofacial clefts. There is a significant clinical variation among different sutural synostoses as well as significant variation within any given single-suture synostosis. Craniosynostosis can be isolated (i.e., nonsyndromic) or occurs as part of a genetic syndrome (e.g., Crouzon, Pfeiffer, Apert, Muenke, and Saethre-Chotzen syndromes). Approximately 85 % of all cases of craniosynostosis are nonsyndromic. Several recent genomic discoveries are elucidating the genetic basis for nonsyndromic cases and implicate the newly identified genes in signaling pathways previously found in syndromic craniosynostosis. Published epidemiologic and phenotypic studies clearly demonstrate that nonsyndromic craniosynostosis is a complex and heterogeneous condition supporting a strong genetic component accompanied by environmental factors that contribute to the pathogenetic network of this birth defect. Large population, rather than single-clinic or hospital-based studies is required with phenotypically homogeneous subsets of patients to further understand the complex genetic, maternal, environmental, and stochastic factors contributing to nonsyndromic craniosynostosis. Learning about these variables is a key in formulating the basis of multidisciplinary and lifelong care for patients with these conditions.

Functional modelling of a novel mutation in BBS5

Background

Bardet-Biedl syndrome (BBS) is an autosomal recessive ciliopathy disorder with 18 known causative genes (BBS1-18). The primary clinical features are renal abnormalities, rod-cone dystrophy, post-axial polydactyly, learning difficulties, obesity and male hypogonadism.

Results

We describe the clinical phenotype in three Saudi siblings in whom we have identified a novel mutation in exon 12 of BBS5 (c.966dupT; p.Ala323CysfsX57). This single nucleotide duplication creates a frame shift results in a predicted elongated peptide. Translation blocking Morpholino oligonucleotides were used to create zebrafish bbs5 morphants. Morphants displayed retinal layering defects, abnormal cardiac looping and dilated, cystic pronephric ducts with reduced cilia expression. Morphants also displayed significantly reduced dextran clearance via the pronephros compared to wildtype embryos, suggesting reduced renal function in morphants. The eye, kidney and heart defects reported in morphant zebrafish resemble the human phenotype of BBS5 mutations. The pathogenicity of the novel BBS5 mutation was determined. Mutant mRNA was unable to rescue pleiotropic phenotypes of bbs5 morphant zebrafish and in cell culture we demonstrate a mislocalisation of mutant BBS5 protein which fails to localise discretely with the basal body.

Conclusions

We conclude that this novel BBS5 mutation has a deleterious function that accounts for the multisystem ciliopathy phenotype seen in affected human patients.

Bariatric surgery in monogenic and syndromic forms of obesity

Currently, no topic is more controversial in bariatric surgery than performing these procedures on children with monogenic and syndromic forms of obesity. The medical community and the caregivers of those patients are struggling to find a solution that can alleviate their suffering and save their life. In all forms of obesity, dieting and physical activity do not result in significant weight loss and is associated with a high rate of weight regain. Additionally, effective medical therapy is not available yet. While there is significant debate about the risks and benefits of bariatric surgery in the adolescent population, there is an increasing number of studies that demonstrate the success of this option for the appropriate patients. Similarly, our experience demonstrated the same success not only in normal children and adolescents but also in those with monogenic and syndromic form of obesity.

Common FSNP variants of fourteen Bardet-Biedl syndrome genes and adult body mass

OBJECTIVE

Bardet-Biedl syndrome (BBS) is a rare monogenic multi-systemic disorder manifesting with marked obesity. Fourteen BBS genes have been identified to date and additional loci are expected. Mutations of several BBS genes were shown to affect fat cell differentiation. The purpose was to Investigate the association between common polymorphisms in all 14 genes as a group and body weight.

DESIGN AND METHODS

We investigated association between tagging single nucleotide polymorphisms (tSNPs) located between 10 kb upstream and downstream from the transcribed sequences of each of 14 BBS genes, and body weight and fat in 2462 adult women from the UK Twins study. Significant results were further tested in a confirmation sample of 2003 women from the same cohort and additionally in the GIANT consortium population (n = 123,865).

RESULTS

105 SNPs in 14 BBS genes were selected and tested in the first cohort of women for association with the body weight and fat related phenotypes, i.e. weight, body mass index (BMI), total body fat (assessed by DEXA), total fat/height(2), and total fat/weight. We used principal component (PC) derived using the latter five traits as a primary phenotype for this study. Of the 105 SNPs, 3 variants in BBS9 and BBS11 showed evidence of nominally significant association with elevated body weight and fat. However, none of the associations survived multiple-testing correction.

CONCLUSIONS

The results suggest that common variation in 14 BBS genes (within or adjacent to the genes) are unlikely to have a substantial effect on body weight and fat in the European population.

Human adipose dynamics and metabolic health

The two types of adipose tissue in humans, white and brown, have distinct developmental origins and functions. Human white adipose tissue plays a pivotal role in maintaining whole-body energy homeostasis by storing triglycerides when energy is in surplus, releasing free fatty acids as a fuel during energy shortage, and secreting adipokines that are important for regulating lipid and glucose metabolism. The size of white adipose mass needs to be kept at a proper set point. Dramatic expansion of white fat mass causes obesity—now become a global epidemic disease—and increases the risk for the development of many life-threatening diseases. The absence of white adipose tissue or abnormal white adipose tissue redistribution leads to lipodystrophy, a condition often associated with metabolic disorders. Brown adipose tissue is a thermogenic organ whose mass is inversely correlated with body mass index and age. Therapeutic approaches targeting adipose tissue have been proven to be effective in improving obesity-related metabolic disorders, and promising new therapies could be developed in the near future.

The globins of cyanobacteria and algae

Approximately, 20 years ago, a haemoglobin gene was identified within the genome of the cyanobacterium Nostoc commune. Haemoglobins have now been confirmed in multiple species of photosynthetic microbes beyond N. commune, and the diversity of these proteins has recently come under increased scrutiny. This chapter summarizes the state of knowledge concerning the phylogeny, physiology and chemistry of globins in cyanobacteria and green algae. Sequence information is by far the best developed and the most rapidly expanding aspect of the field. Structural and ligand-binding properties have been described for just a few proteins. Physiological data are available for even fewer. Although activities such as nitric oxide dioxygenation and oxygen scavenging are strong candidates for cellular function, dedicated studies will be required to complete the story on this intriguing and ancient group of proteins.

A genome-wide association study identifies susceptibility loci for nonsyndromic sagittal craniosynostosis near BMP2 and within BBS9

Sagittal craniosynostosis is the most common form of craniosynostosis, affecting approximately one in 5,000 newborns. We conducted, to our knowledge, the first genome-wide association study for nonsyndromic sagittal craniosynostosis (sNSC) using 130 non-Hispanic case-parent trios of European ancestry (NHW). We found robust associations in a 120-kb region downstream of BMP2 flanked by rs1884302 (P = 1.13 × 10(-14), odds ratio (OR) = 4.58) and rs6140226 (P = 3.40 × 10(-11), OR = 0.24) and within a 167-kb region of BBS9 between rs10262453 (P = 1.61 × 10(-10), OR = 0.19) and rs17724206 (P = 1.50 × 10(-8), OR = 0.22). We replicated the associations to both loci (rs1884302, P = 4.39 × 10(-31) and rs10262453, P = 3.50 × 10(-14)) in an independent NHW population of 172 unrelated probands with sNSC and 548 controls. Both BMP2 and BBS9 are genes with roles in skeletal development that warrant functional studies to further understand the etiology of sNSC.

Mouse models of ciliopathies: the state of the art

The ciliopathies are an apparently disparate group of human diseases that all result from defects in the formation and/or function of cilia. They include disorders such as Meckel-Grüber syndrome (MKS), Joubert syndrome (JBTS), Bardet-Biedl syndrome (BBS) and Alström syndrome (ALS). Reflecting the manifold requirements for cilia in signalling, sensation and motility, different ciliopathies exhibit common elements. The mouse has been used widely as a model organism for the study of ciliopathies. Although many mutant alleles have proved lethal, continued investigations have led to the development of better models. Here, we review current mouse models of a core set of ciliopathies, their utility and future prospects.