Heimler Syndrome.

Heimler syndrome is a rare syndrome associating sensorineural hearing loss with retinal dystrophy and amelogenesis imperfecta due to PEX1 or PEX6 biallelic pathogenic variations. This syndrome is one of the less severe forms of peroxisome biogenesis disorders. In this chapter, we will review clinical, biological, and genetic knowledges about the Heimler syndrome.

Implication of non-coding PAX6 mutations in aniridia.

There is an increasing implication of non-coding regions in pathological processes of genetic origin. This is partly due to the emergence of sophisticated techniques that have transformed research into gene expression by allowing a more global understanding of the genome, both at the genomic, epigenomic and chromatin levels. Here, we implemented the analysis of PAX6, whose coding loss-of-function variants are mainly implied in aniridia, by studying its non-coding regions (untranslated regions, introns and cis-regulatory sequences). In particular, we have taken advantage of the development of high-throughput approaches to screen the upstream and downstream regulatory regions of PAX6 in 47 aniridia patients without identified mutation in the coding sequence. This was made possible through the use of custom targeted resequencing and/or CGH array to analyze the entire PAX6 locus on 11p13. We found candidate variants in 30 of the 47 patients. 9/30 correspond to the well-known described 3' deletions encompassing SIMO and other enhancer elements. In addition, we identified numerous different variants in various non-coding regions, in particular untranslated regions. Among these latter, most of them demonstrated an in vitro functional effect using a minigene strategy, and 12/21 are thus considered as causative mutations or very likely to explain the phenotypes. This new analysis strategy brings molecular diagnosis to more than 90% of our aniridia patients. This study revealed an outstanding mutation pattern in non-coding PAX6 regions confirming that PAX6 remains the major gene for aniridia.

FOXE3 mutations: genotype-phenotype correlations.

Microphthalmia and anophthalmia (MA) are severe developmental eye anomalies, many of which are likely to have an underlying genetic cause. More than 30 genes have been described, each of which is responsible for a small percentage of these anomalies. Among these, is the FOXE3 gene, which was initially described in individuals with dominantly inherited anterior segment dysgenesis and, subsequently, associated with recessively inherited primary aphakia, sclerocornea and microphthalmia. In this work, we describe 8 individuals presenting with an MA phenotype. Among them, 7 are carrying biallelic recessive FOXE3 mutations and 2 of these have novel mutations: p.(Ala78Thr) and p.(Arg104Cys). The last of our patients is carrying in the heterozygous state the recessive p.(Arg90Leu) mutation in the FOXE3 gene. To further understand FOXE3 involvement in this wide spectrum of ocular anomalies with 2 different patterns of inheritance, we reviewed all individuals with ocular abnormalities described in the literature for which a FOXE3 mutation was identified. This review demonstrates that correlations exist between the mutation type, mode of inheritance and the phenotype severity. Furthermore, understanding the genetic basis of these conditions will contribute to overall understanding of eye development, improve the quality of care, genetic counseling and, in future, gene-based therapies.

Dental and extra-oral clinical features in 41 patients with WNT10A gene mutations: A multicentric genotype-phenotype study.

WNT10A gene encodes a canonical wingless pathway signaling molecule involved in cell fate specification as well as morphogenetic patterning of the developing ectoderm, nervous system, skeleton, and tooth. In patients, WNT10A mutations are responsible for ectodermal-derived pathologies including isolated hypo-oligodontia, tricho-odonto-onycho-dermal dysplasia and Schöpf-Schulz-Passarge syndrome (SSPS). Here we describe the dental, ectodermal, and extra-ectodermal phenotypic features of a cohort of 41 patients from 32 unrelated families. Correlations with WNT10A molecular status (heterozygous carrier, compound heterozygous, homozygous) and patient's phenotypes were performed. Mild to severe oligodontia was observed in all patients bearing biallelic WNT10A mutations. However, patients with compound heterozygous mutations presented no significant difference in phenotypes compared with homozygous individuals. Anomalies in tooth morphology were frequently observed with heterozygous patients displaying hypodontia. No signs of SSPS, especially eyelids cysts, were detected in our cohort. Interestingly, extra-ectodermal signs consisted of skeletal, neurological and vascular anomalies, the latter suggesting a wider phenotypic spectrum associated with WNT10A mutations. Indeed, the Wnt pathway plays a crucial role in skeletal development, lipid metabolism, and neurogenesis, potentially explaining patient's clinical manifestations.

Amelogenesis Imperfecta: 1 Family, 2 Phenotypes, and 2 Mutated Genes.

Amelogenesis imperfecta (AI) is a clinically and genetically heterogeneous group of diseases characterized by enamel defects. The authors have identified a large consanguineous Moroccan family segregating different clinical subtypes of hypoplastic and hypomineralized AI in different individuals within the family. Using targeted next-generation sequencing, the authors identified a novel heterozygous nonsense mutation in COL17A1 (c.1873C>T, p.R625*) segregating with hypoplastic AI and a novel homozygous 8-bp deletion in C4orf26 (c.39_46del, p.Cys14Glyfs*18) segregating with hypomineralized-hypoplastic AI in this family. This study highlights the phenotypic and genotypic heterogeneity of AI that can exist even within a single consanguineous family. Furthermore, the identification of novel mutations in COL17A1 and C4orf26 and their correlation with distinct AI phenotypes can contribute to a better understanding of the pathophysiology of AI and the contribution of these genes to amelogenesis.

Value of MRI olfactory bulb evaluation in the assessment of olfactory dysfunction in Bardet-Biedl syndrome.

Olfactory bulb (OB) volume evaluation by magnetic resonance imaging (MRI) has been demonstrated to be related to olfactory dysfunction in many different diseases. Olfactory dysfunction is often overlooked in Bardet-Biedl syndrome (BBS) patients and is rarely objectively evaluated by MRI. We present a series of 20 BBS patients with olfactory dysfunction. The OB was evaluated separately and blindly by two radiologists (SR and SM) with 3 Tesla MRI imaging comparatively to 12 normal control subjects by global visual evaluation and by quantitative measurement of OB volume. In the 12 control cases OB visual evaluation was considered as normal in all cases for radiologist (SR) and in 10 cases for radiologist (SM). In the 20 BBS patients, OB visual evaluation was considered as abnormal in 18 cases for SR and in all cases for SM. OB volumetric evaluation for SR and SM in BBS patients was able to provide significant correlation between BBS and olfactory dysfunction. This study indicates that OB volume evaluation by MRI imaging like structural MRI scan for gray matter modifications demonstrates that olfactory dysfunction in BBS patients is a constant and cardinal symptom integrated in a genetical syndrome with peripheral and central olfactory structure alterations.

[Leucoderma in children: Review of the literature]. / Leucodermies chez l'enfant : revue de la littérature.

BACKGROUND: Leucoderma is a frequent presenting complaint in children and it is sometimes difficult to make a definite diagnostic during the first consultation. The aim of this study is to analyse the diagnoses associated with leucoderma in children in order to propose a practical approach to their differential diagnosis. MATERIAL AND METHODS: We performed a review of the literature using the keywords "leucoderma children review", "leucoderma Ito" and "nevus depigmentosus" in the Medline database. All relevant articles were included. RESULTS: Four hundred and thirty-five articles were retrieved and 179 were analysed. A clinical approach was proposed in 6 articles and investigations in 15 articles. DISCUSSION: Causal diagnosis of leucoderma may frequently be made on clinical grounds by determining the age of onset and distribution of lesions. Nevertheless, some situations require investigation. The literature is limited regarding clinical approaches and examinations in leucoderma. Herein, we present a systematic clinical and laboratory approach to the differential diagnosis of these skin disorders.

Mutation spectrum in BBS genes guided by homozygosity mapping in an Indian cohort.

Bardet-Biedl syndrome (BBS), a ciliopathy disorder with pleiotropic effect manifests primarily as retinal degeneration along with renal insufficiency, polydactyly and obesity. In this study, we have performed homozygosity mapping using NspI 250K affymetrix gene chip followed by mutation screening of the candidate genes located in the homozygous blocks. These regions are prioritized based on the block length and candidature of the genes in BBS and other ciliopathies. Gene alterations in known BBS (22) and other ciliopathy genes such as ALMS1 (2) were seen in 24 of 30 families (80%). Mutations in BBS3 gene, inclusive of a novel recurrent mutation (p.I91T) accounted for 18% of the identified variations. Disease associated polymorphisms p.S70N (BBS2), rs1545 and rs1547 (BBS6) were also observed. This is the first study in Indian BBS patients and homozygosity mapping has proved to be an effective tool in prioritizing the candidate genes in consanguineous pedigrees. The study reveals a different mutation profile in the ciliopathy genes in Indian population and implication of novel loci/genes in 20% of the study group.

Mutation update and uncommon phenotypes in a French cohort of 96 patients with WFS1-related disorders.

WFS1 mutations are responsible for Wolfram syndrome (WS) characterized by juvenile-onset diabetes mellitus and optic atrophy, and for low-frequency sensorineural hearing loss (LFSNHL). Our aim was to analyze the French cohort of 96 patients with WFS1-related disorders in order (i) to update clinical and molecular data with 37 novel affected individuals, (ii) to describe uncommon phenotypes and, (iii) to precise the frequency of large-scale rearrangements in WFS1. We performed quantitative polymerase chain reaction (PCR) in 13 patients, carrying only one heterozygous variant, to identify large-scale rearrangements in WFS1. Among the 37 novel patients, 15 carried 15 novel deleterious putative mutations, including one large deletion of 17,444 base pairs. The analysis of the cohort revealed unexpected phenotypes including (i) late-onset symptoms in 13.8% of patients with a probable autosomal recessive transmission; (ii) two siblings with recessive optic atrophy without diabetes mellitus and, (iii) six patients from four families with dominantly-inherited deafness and optic atrophy. We highlight the expanding spectrum of WFS1-related disorders and we show that, even if large deletions are rare events, they have to be searched in patients with classical WS carrying only one WFS1 mutation after sequencing.

Olfaction evaluation and correlation with brain atrophy in Bardet-Biedl syndrome.

Bardet-Biedl syndrome (BBS) is a well-recognized ciliopathy characterized by cardinal features namely: early onset retinitis pigmentosa, polydactyly, obesity, hypogonadism, renal and cognitive impairment. Recently, disorders of olfaction (anosmia, hyposmia) have been also described in BBS patients. Moreover, morphological brain anomalies have been reported and prompt for further investigations to determine whether they are primary or secondary to peripheral organ involvement (i.e. visual or olfactory neuronal tissue). The objective of this article is to evaluate olfactory disorders in BBS patients and to investigate putative correlation with morphological cerebral anomalies. To this end, 20 BBS patients were recruited and evaluated for olfaction using the University of Pennsylvania Smell Identification Test (UPSIT). All of them underwent a structural magnetic resonance imaging (MRI) scan. We first investigated brain morphological differences between BBS subjects and 14 healthy volunteers. Then, we showed objective olfaction disorders in BBS patients and highlight correlation between gray matter volume reduction and olfaction dysfunction in several brain areas.

Mesoaxial polydactyly is a major feature in Bardet-Biedl syndrome patients with LZTFL1 (BBS17) mutations.

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

Clinical and genetic characterization of Bardet-Biedl syndrome in Tunisia: defining a strategy for molecular diagnosis.

Bardet-Biedl syndrome (BBS, OMIM 209900) is a rare genetic disorder characterized by obesity, retinitis pigmentosa, post axial polydactyly, cognitive impairment, renal anomalies and hypogonadism. The aim of this study is to provide a comprehensive clinical and molecular analysis of a cohort of 11 Tunisian BBS consanguineous families in order to give insight into clinical and genetic spectrum and the genotype-phenotype correlations. Molecular analysis using combined sequence capture and high-throughput sequencing of 30 ciliopathies genes revealed 11 mutations in 11 studied families. Five mutations were novel and six were previously described. Novel mutations included c.1110G>A and c.39delA (p.G13fs*41) in BBS1, c.115+5G>A in BBS2, c.1272+1G>A in BBS6, c.1181_1182insGCATTTATACC in BBS10 (p.S396Lfs*6). Described mutations included c.436C>T (p.R146*) and c.1473+4A>G in BBS1, c.565C> (p.R189*) in BBS2, deletion of exons 4-6 in BBS4, c.149T>G (p.L50R) in BBS5, and c.459+1G>A in BBS8; most frequent mutations were described in BBS1 (4/11, 37%) and BBS2 (2/11, 18%) genes. No phenotype-genotype correlation was evidenced. This data expands the mutations profile of BBS genes in Tunisia and suggests a divergence of the genetic spectrum comparing Tunisian and other populations.

Molecular findings and clinical data in a cohort of 150 patients with anophthalmia/microphthalmia.

Anophthalmia and microphthalmia (AM) are the most severe malformations of the eye, corresponding respectively to reduced size or absent ocular globe. Wide genetic heterogeneity has been reported and different genes have been demonstrated to be causative of syndromic and non-syndromic forms of AM. We screened seven AM genes [GDF6 (growth differentiation factor 6), FOXE3 (forkhead box E3), OTX2 (orthodenticle protein homolog 2), PAX6 (paired box 6), RAX (retina and anterior neural fold homeobox), SOX2 (SRY sex determining region Y-box 2), and VSX2 (visual system homeobox 2 gene)] in a cohort of 150 patients with isolated or syndromic AM. The causative genetic defect was identified in 21% of the patients (32/150). Point mutations were identified by direct sequencing of these genes in 25 patients (13 in SOX2, 4 in RAX, 3 in OTX2, 2 in FOXE3, 1 in VSX2, 1 in PAX6, and 1 in GDF6). In addition eight gene deletions (five SOX2, two OTX2 and one RAX) were identified using a semi-quantitative multiplex polymerase chain reaction (PCR) [quantitative multiplex PCR amplification of short fluorescent fragments (QMPSF)]. The causative genetic defect was identified in 21% of the patients. This result contributes to our knowledge of the molecular basis of AM, and will facilitate accurate genetic counselling.

Long-term follow-up and molecular characterization of a patient with a RECQL4 mutation spectrum disorder.

The follow-up of a man from birth to adulthood, presenting with features both of RAPADILINO and Rothmund-Thomson syndrome (RTS), is described. Molecular studies confirmed the presence of two different mutations, c.2767_2768delTT and c.3061C>T, in the RECQL4 gene. This gene is known to be causative of a spectrum including Baller-Gerold syndrome, RAPADILINO syndrome and RTS. New and rare features such as oral leukoplakia and very prominent hyperkeratotic verrucous papules on both soles are shown. This patient has to date no cancer history despite bearing a truncating mutation at the age of 21 years, which is also unusual.

[Epidemiology of orofacial clefts (1995-2006) in France (Congenital Malformations of Alsace Registry)]. / Épidémiologie des fentes labio-palatines : expérience du Registre de malformations congénitales d'Alsace entre 1995 et 2006.

OBJECTIVES: To review clinical and epidemiologic data of orofacial clefts and to evaluate the efficacy and the impact of prenatal diagnosis. MATERIAL AND METHODS: A population-based retrospective study was carried out on data from the Congenital Malformations of Alsace Registry (France) between 1995 and 2006. RESULTS: A total of 321 orofacial clefts were recorded (overall prevalence, 2.1 per 1000), divided into cleft lip (CL) or cleft lip palate (CLP) (204 cases) and cleft palate (117 cases). The cleft lip and cleft lip palate CL±P sex-ratio was 1.87, whereas the CP sex-ratio was 1. CLs were more often unilateral than CLPs (79% versus 59%). CLs were unilateral in 79% of the cases (60/76), bilateral in 20% of the cases (15/76), and median in 1% (1/76); 55% of the unilateral CLs were right and 45% were left. CLPs were unilateral in 59% of the cases (76/128), bilateral in 39% of the cases (50/128), and median in 2% (2/128); 45% of the unilateral CLPs were right and 55% were left. The 117 CPs were divided into 50 clefts of the total palate (43%) and 67 clefts of the posterior palate (57%); 25 cases (21%) of Pierre Robin sequence were collected. Sixty-six percent of CL±P (134/204) were associated with other congenital anomalies, including chromosome abnormality in 31 cases and identified monogenic syndrome or association in 12 cases. The most frequent chromosome abnormalities were 16 cases of trisomy 13 and 7 cases of trisomy 18. No cases of 22q11.2 microdeletion or duplication were detected among CL±P. Monogenic syndromes were identified in 6% (12/204) of CL±P cases: Van der Woude syndrome (2 cases); CHARGE syndrome (2 cases); ectrodactyly, ectodermal dysplasia, and cleft/lip palate (EEC) syndrome (2 cases); branchiooculofacial (BOF) syndrome (1 case); Treacher-Collins syndrome (1 case); Nager syndrome (1 case); Goldenhar syndrome (1 case); holoprosencephaly spectrum (1 case); and Meckel syndrome (1 case). Forty-two percent of CPs (49/117) were associated with other congenital anomalies; chromosome abnormality was identified in 12 cases and monogenic syndrome was diagnosed in 14 cases. The most frequent chromosome abnormality was 22q11 microdeletion (5 cases). Monogenic syndromes were recognized in 12% of the CP cases (14/117): fragile X syndrome (2 cases), Meckel syndrome (2 cases), Orofaciodigital syndrome type I (OFD1) (1 case), Stickler syndrome (1 case), Larsen syndrome (1 case), Kniest syndrome (1 case), Cornelia de Lange syndrome (1 case), thanatophoric dysplasia (1 case), other unknown bone chondrodysplasia (1 case), Fryns syndrome (1 case), fetal akinesia sequence (1 case), and Silver-Russel syndrome (1 case). Fifty-two percent of CL cases (106/204) were prenatally diagnosed. An increasing tendency was observed between the 1995-2000 and 2001-2006 periods with a detection rate increasing from 47% to 56%. During the whole period, only 1 case of CP was prenatally diagnosed. Eighty-two percent of all cases (263/321) were livebirths; 8 stillbirths were reported (2%); 50 syndromic or associated cases (16%) led to medical abortion (no termination of pregnancy was performed for isolated cleft). CONCLUSION: Orofacial clefts are a frequent malformation with a total prevalence of 2.1 per 1000 total births. Sonbographic prenatal diagnosis of orofacial clefts remains difficult with a mean detection rate about 50% for CL±P and is extremely rare for CP. Associated malformations and genetic syndromes are frequent and require a systematic survey. This study also highlights the different pathogenic background of CL±P compared to CP, regarding the sex-ratio and the proportion and type of associated malformations.

Differentiating Alström from Bardet-Biedl syndrome (BBS) using systematic ciliopathy genes sequencing.

INTRODUCTION: Early onset retinal degeneration associated with obesity can present a diagnostic challenge in paediatric ophthalmology practice. Clinical overlap between Bardet-Biedl syndrome (BBS) and Alström syndrome has been described, although the two entities are genetically distinct. To date, 16 genes are known to be associated with BBS (BBS1-16) and only one gene has been identified for Alström syndrome (ALMS1). MATERIALS AND METHODS: In collaboration with the French National Center for Sequencing (CNS, Evry), all coding exons and flanking introns were sequenced for 27 ciliopathy genes (BBS1-12, MGC1203, TTC21b, AHI1, NPHP2-8 (NPHP6=BBS14), MKS1(BBS13), MKS3, C2ORF86, SDCCAG8, ALMS1) in 96 patients referred with a clinical diagnosis of BBS. ALMS1 gene analysis included sequencing of all coding exons. RESULTS: BBS known gene mutations were found in 44 patients (36 with two mutations and 8 heterozygous). ALMS1 mutations were found in four cases. The rate of ALMS1 mutations among patients suspected of having BBS was 4.2%. DISCUSSION: Clinically, all four patients presented early-onset severe retinal degeneration with congenital nystagmus associated with obesity. The difficult early differential diagnosis between the two syndromes is outlined. One mutation had already been reported (c.11310delAGAG/p.R3770fsX) and three were novel (c.2293C > T/p.Q765X, c.6823insA/p.R2275fsX, c.9046delA/p.N3016fsX). CONCLUSIONS: Ciliopathy genes sequencing can be very helpful in providing a timely diagnosis in this group of patients, hence appropriate genetic counselling for families and adequate medical follow-up for affected children.

Mutations in SDCCAG8/NPHP10 Cause Bardet-Biedl Syndrome and Are Associated with Penetrant Renal Disease and Absent Polydactyly.

The ciliopathies are an expanding group of disorders caused by mutations in genes implicated in the biogenesis and function of primary cilia. Bardet-Biedl syndrome (BBS) is a model ciliopathy characterized by progressive retinal degeneration, obesity, polydactyly, cognitive impairment, kidney anomalies and hypogonadism. Mutations in SDCCAG8(NPHP10) were described recently in patients with nephronophthisis and retinal degeneration (Senior-Loken syndrome; SLS). Given the phenotypic and genetic overlap between known ciliopathy genes, we hypothesized that mutations in SDCCAG8 might also contribute alleles to more severe, multisystemic ciliopathies. We performed genetic and phenotypic analyses of 2 independent BBS cohorts. Subsequent to mutation screening, we made a detailed phenotypic analysis of 5 families mutated for SDCCAG8 (3 homozygous and 2 compound heterozygous mutations) and conducted statistical analyses across both cohorts to examine possible phenotype-genotype correlations with mutations at this locus. All patients with mutations in SDCCAG8 fulfilled the diagnostic criteria for BBS (retinal degeneration, obesity, cognitive defects, renal failure, hypogonadism). Interestingly, none of the patients with primary SDCCAG8 mutations had polydactyly, a frequent but not obligatory BBS feature. In contrast, the same patients displayed early-onset renal failure, obesity, as well as recurrent pulmonary and ENT infections. Comparison of the phenotypes of these families with our entire BBS cohort indicated that renal impairment and absent polydactyly correlated significantly with causal SDCCAG8 mutations. Thus, SDCCAG8 mutations are sufficient to cause BBS in 1-2% of our combined cohorts, and define this gene as the sixteenth BBS locus (BBS16). The absence of polydactyly and the concomitant, apparently fully penetrant association with early kidney failure represents the first significant genotype-phenotype correlation in BBS that potentially represents an indicator for phenotype-driven priority screening and informs specific patient management.

Hippocampal dysgenesis and variable neuropsychiatric phenotypes in patients with Bardet-Biedl syndrome underline complex CNS impact of primary cilia.

The Bardet-Biedl syndrome (BBS) is a rare ciliopathy clinically defined by the association of retinitis pigmentosa, polydactyly, obesity, kidney disease and cognitive impairment. The cognitive functioning, behavioral phenotype, prevalence of psychiatric diseases and memory performances of a cohort of 34 patients with BBS were evaluated and a systemic brain magnetic resonance imaging (MRI) was performed. The patients' cognitive functioning was of marked variable efficiency ranging from normal to disabling performances. Neuropsychological disorders such as slow thought process, attention difficulties and obsessive-compulsive traits were observed. Our main finding was hippocampal dysgenesis, diagnosed by MRI, found in 42.31% of the patients in this cohort. Moreover, we show that BBS proteins are expressed in the human hippocampus and in the human brain in the normal subject. Recent literature in the murine model shows that hippocampal neurogenesis, in particular in the adult mouse, requires an intact primary cilia. These results encourage us to further investigate the possible role of BBS proteins in the hippocampus and related central nervous system structures.