Audiological phenotyping evaluation in KBG syndrome: Description of a multicenter review

OBJECTIVES

Our objective was to reinforce clinical knowledge of hearing impairment in KBG syndrome. KBG syndrome is a rare genetic disorder due to monoallelic pathogenic variations of ANKRD11.The typical phenotype includes facial dysmorphism, costal and spinal malformation and developmental delay. Hearing loss in KBG patients has been reported for many years, but no study has evaluated audiological phenotyping from a clinical and an anatomical point of view.

METHODS

This French multicenter study included 32 KBG patients with retrospective collection of data on audiological features, ear imaging and genetic investigations.

RESULTS

We identified a typical audiological profil in KBG syndrome: conductive (71%), bilateral (81%), mild to moderate (84%) and stable (69%) hearing loss, with some audiological heterogeneity. Among patients with an abnormality on CT imaging (55%), ossicular chain impairment (67%), fixation of the stapes footplate (33%) and inner-ear malformations (33%) were the most common abnormalities.

CONCLUSION

We recommend a complete audiological and radiological evaluation and an ENT-follow up in all patients presenting with KBG Syndrome. Imaging evaluation is necessary to determine the nature of lesions in the middle and inner ear.

Better Understanding of the Metamorphosis of Pregnancy (BUMP): protocol for a digital feasibility study in women from preconception to postpartum

The Better Understanding the Metamorphosis of Pregnancy (BUMP) study is a longitudinal feasibility study aimed to gain a deeper understanding of the pre-pregnancy and pregnancy symptom experience using digital tools. The present paper describes the protocol for the BUMP study. Over 1000 participants are being recruited through a patient provider-platform and through other channels in the United States (US). Participants in a preconception cohort (BUMP-C) are followed for 6 months, or until conception, while participants in a pregnancy cohort (BUMP) are followed into their fourth trimester. Participants are provided with a smart ring, a smartwatch (BUMP only), and a smart scale (BUMP only) alongside cohort-specific study apps. Participant centric engagement strategies are used that aim to co-design the digital approach with participants while providing knowledge and support. The BUMP study is intended to lay the foundational work for a larger study to determine whether participant co-designed digital tools can be used to detect, track and return multimodal symptoms during the perinatal window to inform individual level symptom trajectories.

SATB2-associated syndrome: characterization of skeletal features and of bone fragility in a prospective cohort of 19 patients

Background

Individuals with pathogenic variants in SATB2 display intellectual disability, speech and behavioral disorders, dental abnormalities and often features of Pierre Robin sequence. SATB2 encodes a transcription factor thought to play a role in bone remodeling. The primary aim of our study was to systematically review the skeletal manifestations of SATB2-associated syndrome. For this purpose, we performed a non-interventional, multicenter cohort study, from 2017 to 2018. We included 19 patients, 9 females and 10 males ranging in age from 2 to 19 years-old. The following data were collected prospectively for each patient: clinical data, bone markers and calcium and phosphate metabolism parameters, skeletal X-rays and bone mineral density.

Results

Digitiform impressions were present in 8/14 patients (57%). Vertebral compression fractures affected 6/17 patients (35%). Skeletal demineralization (16/17, 94%) and cortical thinning of vertebrae (15/17) were the most frequent radiological features at the spine. Long bones were generally demineralized (18/19). The distal phalanges were short, thick and abnormally shaped. C-telopeptide (CTX) and Alkaline phosphatase levels were in the upper normal values and osteocalcin and serum procollagen type 1 amino-terminal propeptide (P1NP) were both increased. Vitamin D insufficiency was frequent (66.7%).

Conclusion

We conclude that SATB2 pathogenic variants are responsible for skeletal demineralization and osteoporosis. We found increased levels of bone formation markers, supporting the key role of SATB2 in osteoblast differentiation. These results support the need for bone evaluation in children and adult patients with SATB2-associated syndrome (SAS).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02229-5.

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.

Wiedemann-Steiner syndrome as a major cause of syndromic intellectual disability: A study of 33 French cases

Wiedemann-Steiner syndrome (WSS) is a rare syndromic condition in which intellectual disability (ID) is associated with hypertrichosis cubiti, short stature, and characteristic facies. Following the identification of the causative gene (KMT2A) in 2012, only 31 cases of WSS have been described precisely in the literature. We report on 33 French individuals with a KMT2A mutation confirmed by targeted gene sequencing, high-throughput sequencing or exome sequencing. Patients' molecular and clinical features were recorded and compared with the literature data. On the molecular level, we found 29 novel mutations. We observed autosomal dominant transmission of WSS in 3 families and mosaicism in one family. Clinically, we observed a broad phenotypic spectrum with regard to ID (mild to severe), the facies (typical or not of WSS) and associated malformations (bone, cerebral, renal, cardiac and ophthalmological anomalies). Hypertrichosis cubiti that was supposed to be pathognomonic in the literature was found only in 61% of our cases. This is the largest series of WSS cases yet described to date. A majority of patients exhibited suggestive features, but others were less characteristic, only identified by molecular diagnosis. The prevalence of WSS was higher than expected in patients with ID, suggesting than KMT2A is a major gene in ID.

MED13L-related intellectual disability: involvement of missense variants and delineation of the phenotype

Molecular anomalies in MED13L, leading to haploinsufficiency, have been reported in patients with moderate to severe intellectual disability (ID) and distinct facial features, with or without congenital heart defects. Phenotype of the patients was referred to "MED13L haploinsufficiency syndrome." Missense variants in MED13L were already previously described to cause the MED13L-related syndrome, but only in a limited number of patients. Here we report 36 patients with MED13L molecular anomaly, recruited through an international collaboration between centers of expertise for developmental anomalies. All patients presented with intellectual disability and severe language impairment. Hypotonia, ataxia, and recognizable facial gestalt were frequent findings, but not congenital heart defects. We identified seven de novo missense variations, in addition to protein-truncating variants and intragenic deletions. Missense variants clustered in two mutation hot-spots, i.e., exons 15-17 and 25-31. We found that patients carrying missense mutations had more frequently epilepsy and showed a more severe phenotype. This study ascertains missense variations in MED13L as a cause for MED13L-related intellectual disability and improves the clinical delineation of the condition.

A series of 38 novel germline and somatic mutations of NIPBL in Cornelia de Lange syndrome

Cornelia de Lange syndrome is a multisystemic developmental disorder mainly related to de novo heterozygous NIPBL mutation. Recently, NIPBL somatic mosaicism has been highlighted through buccal cell DNA study in some patients with a negative molecular analysis on leukocyte DNA. Here, we present a series of 38 patients with a Cornelia de Lange syndrome related to a heterozygous NIPBL mutation identified by Sanger sequencing. The diagnosis was based on the following criteria: (i) intrauterine growth retardation and postnatal short stature, (ii) feeding difficulties and/or gastro-oesophageal reflux, (iii) microcephaly, (iv) intellectual disability, and (v) characteristic facial features. We identified 37 novel NIPBL mutations including 34 in leukocytes and 3 in buccal cells only. All mutations shown to have arisen de novo when parent blood samples were available. The present series confirms the difficulty in predicting the phenotype according to the NIPBL mutation. Until now, somatic mosaicism has been observed for 20 cases which do not seem to be consistently associated with a milder phenotype. Besides, several reports support a postzygotic event for those cases. Considering these elements, we recommend a first-line buccal cell DNA analysis in order to improve gene testing sensitivity in Cornelia de Lange syndrome and genetic counselling.

Genetic counselling difficulties and ethical implications of incidental findings from array-CGH: a 7-year national survey

Microarray-based comparative genomic hybridization (aCGH) is commonly used in diagnosing patients with intellectual disability (ID) with or without congenital malformation. Because aCGH interrogates with the whole genome, there is a risk of being confronted with incidental findings (IF). In order to anticipate the ethical issues of IF with the generalization of new genome-wide analysis technologies, we questioned French clinicians and cytogeneticists about the situations they have faced regarding IF from aCGH. Sixty-five IF were reported. Forty corresponded to autosomal dominant diseases with incomplete penetrance, 7 to autosomal dominant diseases with complete penetrance, 14 to X-linked diseases, and 4 were heterozygotes for autosomal recessive diseases with a high prevalence of heterozygotes in the population. Therapeutic/preventive measures or genetic counselling could be argued for all cases except four. These four IF were intentionally not returned to the patients. Clinicians reported difficulties in returning the results in 29% of the cases, mainly when the question of IF had not been anticipated. Indeed, at the time of the investigation, only 48% of the clinicians used consents mentioning the risk of IF. With the emergence of new technologies, there is a need to report such national experiences; they show the importance of pre-test information on IF.

Clinical spectrum of eye malformations in four patients with Mowat-Wilson syndrome

Mowat-Wilson syndrome (MWS) is a rare genetic syndrome characterized by a specific facial gestalt, intellectual deficiency, Hirschsprung disease and multiple congenital anomalies. Heterozygous mutations or deletions in the zinc finger E-box-binding homeobox2 gene (ZEB2) cause MWS. ZEB2 encodes for Smad-interacting protein 1, a transcriptional co-repressor involved in TGF-beta and BMP pathways and is strongly expressed in early stages of development in mice. Eye abnormalities have rarely been described in patients with this syndrome. Herein, we describe four patients (two males and two females; mean age 7 years) with MWS and eye malformations. Ocular anomalies included, iris/retinal colobomas, atrophy or absence of the optic nerve, hyphema, and deep refraction troubles, sometimes with severe visual consequences. All eye malformations were asymmetric and often unilateral and all eye segments were affected, similarly to the nine MWS cases with ophthalmological malformations previously reported (iris/chorioretinal/optic disc coloboma, optic nerve atrophy, retinal epithelium atrophy, cataract, and korectopia). In human embryo, ZEB2 is expressed in lens and neural retina. Using the present report and data from the literature, we set out to determine whether or not the presence of eye manifestations could be due to specific type or location of mutations. We concluded that the presence of eye malformations, although a rare feature in MWS, should be considered as a part of the clinical spectrum of the condition.

Search for ReCQL4 mutations in 39 patients genotyped for suspected Rothmund-Thomson/Baller-Gerold syndromes

Three overlapping conditions, namely Rothmund-Thomson (RTS), Baller-Gerold (BGS) and RAPADILINO syndromes, have been attributed to RECQL4 mutations. Differential diagnoses depend on the clinical presentation, but the numbers of known genes remain low, leading to the widespread prescription of RECQL4 sequencing. The aim of our study was therefore to determine the best clinical indicators for the presence of RECQL4 mutations in a series of 39 patients referred for RECQL4 molecular analysis and belonging to the RTS (27 cases) and BGS (12 cases) spectrum. One or two deleterious RECQL4 mutations were found in 10/27 patients referred for RTS diagnosis. Clinical and molecular reevaluation led to a different diagnosis in 7/17 negative cases, including Clericuzio-type poikiloderma with neutropenia, hereditary sclerosing poikiloderma, and craniosynostosis/anal anomalies/porokeratosis. No RECQL4 mutations were found in the BGS group without poikiloderma, confirming that RECQL4 sequencing was not indicated in this phenotype. One chromosomal abnormality and one TWIST mutation was found in this cohort. This study highlights the search for differential diagnoses before the prescription of RECQL4 sequencing in this clinically heterogeneous group. The combination of clinically defined subgroups and next-generation sequencing will hopefully bring to light new molecular bases of syndromes with poikiloderma, as well as BGS without poikiloderma.

Community engagement in US biobanking: multiplicity of meaning and method

BACKGROUND/AIMS

Efforts to improve individual and population health increasingly rely on large-scale collections of human biological specimens and associated data. Such collections or 'biobanks' are hailed as valuable resources for facilitating translational biomedical research. However, biobanks also raise important ethical considerations, such as whether, how and why biobanks might engage with those who contributed specimens. This paper examines perceptions and practices of community engagement (CE) among individuals who operate 6 diverse biobanks in the US.

METHODS

Twenty-four people from a diverse group of 6 biobanks were interviewed in-person or via telephone from March to July 2011. Interview transcripts were coded and analyzed for common themes.

RESULTS

Emergent themes include how biobank personnel understand 'community' and CE as it pertains to biobank operations, information regarding the diversity of practices of CE, and the reasons why biobanks conduct CE.

CONCLUSION

Despite recommendations from federal agencies to conduct CE, the interpretation of CE varies widely among biobank employees, ultimately affecting how CE is practiced and what goals are achieved.

Systematic molecular and cytogenetic screening of 100 patients with marfanoid syndromes and intellectual disability

The association of marfanoid habitus (MH) and intellectual disability (ID) has been reported in the literature, with overlapping presentations and genetic heterogeneity. A hundred patients (71 males and 29 females) with a MH and ID were recruited. Custom-designed 244K array-CGH (Agilent®; Agilent Technologies Inc., Santa Clara, CA) and MED12, ZDHHC9, UPF3B, FBN1, TGFBR1 and TGFBR2 sequencing analyses were performed. Eighty patients could be classified as isolated MH and ID: 12 chromosomal imbalances, 1 FBN1 mutation and 1 possibly pathogenic MED12 mutation were found (17%). Twenty patients could be classified as ID with other extra-skeletal features of the Marfan syndrome (MFS) spectrum: 4 pathogenic FBN1 mutations and 4 chromosomal imbalances were found (2 patients with both FBN1 mutation and chromosomal rearrangement) (29%). These results suggest either that there are more loci with genes yet to be discovered or that MH can also be a relatively non-specific feature of patients with ID. The search for aortic complications is mandatory even if MH is associated with ID since FBN1 mutations or rearrangements were found in some patients. The excess of males is in favour of the involvement of other X-linked genes. Although it was impossible to make a diagnosis in 80% of patients, these results will improve genetic counselling in families.

Intragenic rearrangements in LARGE and POMGNT1 genes in severe dystroglycanopathies

Dystroglycanopathies are a heterogeneous group of muscular dystrophies with autosomal recessive inheritance characterized by abnormal glycosylation of alpha-dystroglycan. The most severe phenotypes are Walker-Warburg Syndrome (WWS) and muscle-eye-brain disease (MEB) presenting with lissencephaly type II (LIS II) and in which muscular dystrophy is associated with mental retardation and eye abnormalities. To date, six distinct genes, POMT1, POMT2, POMGNT1, FKTN, FKRP, LARGE and recently in one case DPM3, have been shown to be involved in dystroglycanopathies. Genomic sequencing alone is still frequently used for diagnosis purpose, not allowing detection of intragenic rearrangements at the heterozygous state contrarily to RNA analysis, quantitative PCR and CGH array analysis. These latter methods enabled us to identify four new intragenic rearrangements in the LARGE gene in three fetuses with WWS, born to two unrelated families: deletion of exons 9-10 and duplication of introns 1-4 for the first family and deletion of exons 4 and 7 for the second one; and a deletion of the last six exons of the POMGNT1 gene in two unrelated MEB patients. Genomic dosage studies using emerging tools such as CGH array should be included in routine molecular analysis of dystroglycanopathies, not only for the screening of the LARGE gene in which this kind of mutation seems to be more frequent than point mutations, but also for the other involved genes, especially in severe clinical cases.

IRF6 Screening of Syndromic and a priori Non-Syndromic Cleft Lip and Palate Patients: Identification of a New Type of Minor VWS Sign

Van der Woude syndrome (VWS), caused by dominant IRF6 mutation, is the most common cleft syndrome. In 15% of the patients, lip pits are absent and the phenotype mimics isolated clefts. Therefore, we hypothesized that some of the families classified as having non-syndromic inherited cleft lip and palate could have an IRF6 mutation. We screened in total 170 patients with cleft lip with or without cleft palate (CL/P): 75 were syndromic and 95 were a priori part of multiplex non-syndromic families. A mutation was identified in 62.7 and 3.3% of the patients, respectively. In one of the 95 a priori non-syndromic families with an autosomal dominant inheritance (family B), new insights into the family history revealed the presence, at birth, of lower lip pits in two members and the diagnosis was revised as VWS. A novel lower lip sign was observed in one individual in this family. Interestingly, a similar lower lip sign was also observed in one individual from a 2nd family (family A). This consists of 2 nodules below the lower lip on the external side. In a 3rd multiplex family (family C), a de novo mutation was identified in an a priori non-syndromic CL/P patient. Re-examination after mutation screening revealed the presence of a tiny pit-looking lesion on the inner side of the lower lip leading to a revised diagnosis of VWS. On the basis of this data, we conclude that IRF6 should be screened when any doubt rises about the normality of the lower lip and also if a non-syndromic cleft lip patient (with or without cleft palate) has a family history suggestive of autosomal dominant inheritance.

Use of marginal organs in kidney transplantation for marginal recipients: too close to the margins of safety?

Objective

Due to organ shortage, average waiting time for a kidney in Germany is about 4 years after start of dialysis. Number of kidney grafts recovered can only be maintained by accepting older and expanded criteria donors. The aim of this study was to analyse the impact of donor and recipient risk on kidney long-term function.

Methods

All deceased kidney transplantations were considered. We retrospectively studied 332 patients between 2002 and 2006; divided in 4 groups reflecting donor and recipient risk.

Results

Non-marginal recipients were less likely to receive a marginal organ (69 of 207, 33%) as compared to marginal recipients, of whom two-thirds received a marginal organ (p < 0.0001). Graft function significantly differed between the groups, but detrimental effect of marginal recipient status on eGFR after 12 months (-6 ml/min/1.73 qm, 95% CI -2 to -9) was clearly smaller than the effect of marginal donor status (-10 ml/min/1.73 qm, 95% CI -7 to -14).

Conclusions

As we were able to show expanded criteria donor has a far bigger effect on long-term graft function than the "extra risk" recipient. Although there have been attempts to define groups of recipients who should be offered ECD kidneys primarily the discussion is still ongoing.

Identification of 28 novel mutations in the Bardet-Biedl syndrome genes: the burden of private mutations in an extensively heterogeneous disease

Bardet-Biedl syndrome (BBS), an emblematic disease in the rapidly evolving field of ciliopathies, is characterized by pleiotropic clinical features and extensive genetic heterogeneity. To date, 14 BBS genes have been identified, 3 of which have been found mutated only in a single BBS family each (BBS11/TRIM32, BBS13/MKS1 and BBS14/MKS4/NPHP6). Previous reports of systematic mutation detection in large cohorts of BBS families (n > 90) have dealt only with a single gene, or at most small subsets of the known BBS genes. Here we report extensive analysis of a cohort of 174 BBS families for 12/14 genes, leading to the identification of 28 novel mutations. Two pathogenic mutations in a single gene have been found in 117 families, and a single heterozygous mutation in 17 families (of which 8 involve the BBS1 recurrent mutation, M390R). We confirm that BBS1 and BBS10 are the most frequently mutated genes, followed by BBS12. No mutations have been found in BBS11/TRIM32, the identification of which as a BBS gene only relies on a single missense mutation in a single consanguineous family. While a third variant allele has been observed in a few families, they are in most cases missenses of uncertain pathogenicity, contrasting with the type of mutations observed as two alleles in a single gene. We discuss the various strategies for diagnostic mutation detection, including homozygosity mapping and targeted arrays for the detection of previously reported mutations.

Experimental study comparing meshes made of polypropylene, polypropylene + polyglactin and polypropylene + titanium: inflammatory cytokines, histological changes and morphometric analysis of collagen

PURPOSE

Incisional hernia occurs in approximately 11% of all laparotomies. Changes in collagen have been closely implicated in its pathogenesis. The high recurrence rate (45-54%) after primary suture has stimulated the development of meshes. Currently, meshes are the biomaterials implant group most used in medicine. This study aims to compare the serum and tissue inflammatory responses and collagen deposition caused by meshes made of polypropylene, polypropylene + polyglactin and polypropylene + titanium.

METHODS

Thirty Wistar rats were divided into three groups. In group I, a high-density polypropylene mesh was positioned on the abdominal wall. In groups II and III, low-density meshes were used in associations with polyglactin and titanium, respectively. Immediately before the operation and on the first, third and fortieth postoperative days, pro-inflammatory cytokines were assayed. On the 40th postoperative day, the region of the inserted prosthesis was biopsied. The tissue inflammatory reaction was evaluated using a scale for objective scoring. For collagen, picrosirius was used with data reading using the Image Tool computer software.

RESULTS

Cytokines: there were no statistically significant differences between the groups.

HISTOLOGY

on the 40th postoperative day in group I, there were fewer inflammatory tissue response and greater collagen deposition (P < 0.01). In group II, there were greater inflammatory tissue response and less collagen deposition (P < 0.01). Group III presented intermediate values between groups I and II.

CONCLUSIONS

There were no significant differences in cytokine levels between the groups in the present study. In the animals with the polypropylene + polyglactin mesh implant there was the most intense inflammatory process with lower tissue maturation and collagen deposition on the 40th postoperative day. The polypropylene mesh presented a less severe late inflammatory process, with greater tissue maturation and collagen deposition. The polypropylene + titanium mesh presented intermediate values between the others.

Mutational spectrum of CDKL5 in early-onset encephalopathies: a study of a large collection of French patients and review of the literature

The CDKL5 gene has been implicated in the molecular etiology of early-onset intractable seizures with infantile spasms (IS), severe hypotonia and atypical Rett syndrome (RTT) features. So far, 48 deleterious alleles have been reported in the literature. We screened the CDKL5 gene in a cohort of 177 patients with early-onset seizures, including 30 men and 10 girls with Aicardi syndrome. The screening was negative for all men as well as for women with Aicardi syndrome, excluding the CDKL5 gene as a candidate for this neurodevelopmental disorder. We report 11 additional de novo mutations in CDKL5 in female patients. For the first time, the MLPA approach allowed the identification of a partial deletion encompassing the promoter and the first two exons of CDKL5. The 10-point mutations consist of five missenses (with recurrent amino acid changes at p.Ala40 and p.Arg178), four splicing variants and a 1-base pair duplication. We present a review of all mutated alleles published in the literature. In our study, the overall frequency of mutations in CDKL5 in women with early-onset seizures is around 8.6%, a result comparable with previous reports. Noteworthy, the CDKL5 mutation rate is high (28%) in women with early-onset seizures and IS.

[Genetics of mental retardation]

Mental retardation affects nearly 3 % of the population. The causes of these disorders are various and are often not identified. Recent advances focused on the molecular basis of mental retardation. Nearly half of mental retardation syndromes have a genetic origin and the description of molecular, cytogenetic and metabolic alterations in these disorders led to the development of diagnostic tools. Indeed, identifying the precise origin of the mental retardation allows to improve patient care and to refine the prognosis. Moreover, these molecular tools will help the geneticist to evaluate the recurrence risk in the family in the genetic counseling step. On a fundamental point of view, the knowledge of molecular basis of mental retardation will help to understand the biological pathway which constitutes the first step before therapeutic strategies. Every patient with mental retardation should be investigated for causal origin of the disease. We will detail the diagnostic methods necessary to investigate a patient presenting with mental retardation. Then different examples of syndromes including a mental retardation will be chosen to illustrate different clinical situations.

MEF2C haploinsufficiency caused by either microdeletion of the 5q14.3 region or mutation is responsible for severe mental retardation with stereotypic movements, epilepsy and/or cerebral malformations

BACKGROUND

Over the last few years, array-comparative genomic hybridisation (CGH) has considerably improved our ability to detect cryptic unbalanced rearrangements in patients with syndromic mental retardation.

METHOD

Molecular karyotyping of six patients with syndromic mental retardation was carried out using whole-genome oligonucleotide array-CGH.

RESULTS

5q14.3 microdeletions ranging from 216 kb to 8.8 Mb were detected in five unrelated patients with the following phenotypic similarities: severe mental retardation with absent speech, hypotonia and stereotypic movements. Facial dysmorphic features, epilepsy and/or cerebral malformations were also present in most of these patients. The minimal common deleted region of these 5q14 microdeletions encompassed only MEF2C, the gene for a protein known to act in brain as a neurogenesis effector, which regulates excitatory synapse number. In a patient with a similar phenotype, an MEF2C nonsense mutation was subsequently identified.

CONCLUSION

Taken together, these results strongly suggest that haploinsufficiency of MEF2C is responsible for severe mental retardation with stereotypic movements, seizures and/or cerebral malformations.

Impact of modulators of mitochondrial ATP-sensitive potassium channel (mitoK(ATP)) on hypoxic pulmonary vasoconstriction

Previously, we demonstrated that hypoxic pulmonary vasoconstriction (HPV) of intra-acinar arteries (IAA) requires mitochondrial complex II (= succinate dehydrogenase, SDH) activity (citeauthor ch41:paddenberg2006, Respir Res, 7:93, citeyear ch41:paddenberg2006). Interestingly, SDH subunits A and B have recently been described as components of a multiprotein mitochondrial ATP-sensitive potassium channel (mitoK(ATP)), together with mitochondrial ATP-binding cassette protein-1, adenine nucleotide translocator (ANT), ATP synthase, and phosphate carrier (citeauthor ch41:ardehali2004, Proc Natl Acad Sci USA, 101(32):11880-5, citeyear ch41:ardehali2004). Hence, we tested the hypothesis that such an SDH-containing mitoK(ATP) is involved in HPV. For this purpose, the impact of modulators of mitoK(ATP) on HPV of IAA was studied videomorphometrically in precision cut murine lung slices. Inhibitors of mitoK(ATP) (glibenclamide, 5-hydroxydecanoate) completely suppressed HPV, mitoK(ATP) activators (pinacidil, diazoxide) even induced vasodilatation, and ANT inhibitors (bongkrekic acid, atractyloside) attenuated HPV. This pharmacological profile differs clearly from that described for mitoK(ATP). Accordingly, co-immunoprecipitation experiments provided no evidence for association of complex II subunits SDH-A, -B and -C with ANT, ATP synthase or cytochrome c oxidase in murine heart mitochondria. Hence, it is likely that the inhibitory effects on HPV that we observed in our experiments result from modulation of several mitochondrial protein complexes independently involved in the signalling cascade such as ROS-producing complex II and ANT-regulated mitochondrial permeability transition pore.

Clinical and molecular delineation of the 17q21.31 microdeletion syndrome

BACKGROUND

The chromosome 17q21.31 microdeletion syndrome is a novel genomic disorder that has originally been identified using high resolution genome analyses in patients with unexplained mental retardation.

AIM

We report the molecular and/or clinical characterisation of 22 individuals with the 17q21.31 microdeletion syndrome.

RESULTS

We estimate the prevalence of the syndrome to be 1 in 16,000 and show that it is highly underdiagnosed. Extensive clinical examination reveals that developmental delay, hypotonia, facial dysmorphisms including a long face, a tubular or pear-shaped nose and a bulbous nasal tip, and a friendly/amiable behaviour are the most characteristic features. Other clinically important features include epilepsy, heart defects and kidney/urologic anomalies. Using high resolution oligonucleotide arrays we narrow the 17q21.31 critical region to a 424 kb genomic segment (chr17: 41046729-41470954, hg17) encompassing at least six genes, among which is the gene encoding microtubule associated protein tau (MAPT). Mutation screening of MAPT in 122 individuals with a phenotype suggestive of 17q21.31 deletion carriers, but who do not carry the recurrent deletion, failed to identify any disease associated variants. In five deletion carriers we identify a <500 bp rearrangement hotspot at the proximal breakpoint contained within an L2 LINE motif and show that in every case examined the parent originating the deletion carries a common 900 kb 17q21.31 inversion polymorphism, indicating that this inversion is a necessary factor for deletion to occur (p<10(-5)).

CONCLUSION

Our data establish the 17q21.31 microdeletion syndrome as a clinically and molecularly well recognisable genomic disorder.