Molekulare Karyotypisierung in der Diagnostik neurokognitiver Entwicklungsst?rungen

Establishing an etiological diagnosis in patients with developmental neurocognitive disorders involving intellectual disability represents a common challenge in clinical genetics. Although more than 400?monogenic diseases with intellectual disability as a trait have been delineated, chromosomal disorders represent the majority of known causes to date. Excluding Down syndrome, high-resolution molecular karyotyping is able to reveal a causative chromosomal imbalance in 18% of unselected patients, while microscopic karyotyping would detect a causal aberration in only 4% of cases. Increasing resolution, however, also increases the number of benign copy number variants detected, which may hamper the interpretation of results. Indicators of disease associated copy number changes include aberration size, gene content and segregation of the aberration with the phenotype within a family. Ultimately, causality can only be proven when multiple cases with a similar genotype and phenotype have been observed.     

Dissecting the genotype in syndromic intellectual disability using whole exome sequencing in addition to genome-wide copy number analysis

When a known microimbalance affecting multiple genes is detected in a patient with syndromic intellectual disability, it is usually presumed causative for all observed features. Whole exome sequencing (WES) allows questioning this assumption. In this study of three families with children affected by unexplained syndromic intellectual disability, genome-wide copy number and subsequent analyses revealed a de novo maternal 1.1 Mb microdeletion in the 14q32 imprinted region causing a paternal UPD(14)-like phenotype, and two inherited 22q11.21 microduplications of 2.5 or 2.8 Mb. In patient 1 carrying the 14q32 microdeletion, tall stature and renal malformation were unexplained by paternal UPD(14), and there was no altered DLK1 expression or unexpected methylation status. By WES and filtering with a mining tool, a novel FBN1 missense variant was found in patient 1 and his mother, who both showed clinical features of Marfan syndrome by thorough anthropometric assessment, and a novel EYA1 missense variant as a probable cause of the renal malformation in the patient. In patient 2 with the 22q11.21 microduplication syndrome, skin hypo- and hyperpigmentation and two malignancies were only partially explained. By WES, compound heterozygous BLM stop founder mutations were detected causing Bloom syndrome. In male patient 3 carrying a 22q11.21 microduplication inherited from his unaffected father, WES identified a novel missense variant in the OPHN1 X-linked intellectual disability gene inherited from the unaffected mother as a possible additional cause for developmental delay. Thus, WES seems warranted in patients carrying microdeletions or microduplications, who have unexplained clinical features or microimbalances inherited from an unaffected parent.     

Revealing the Complexity of a Monogenic Disease: Rett Syndrome Exome Sequencing

Rett syndrome (OMIM#312750) is a monogenic disorder that may manifest as a large variety of phenotypes ranging from very severe to mild disease. Since there is a weak correlation between the mutation type in the Xq28 disease-gene MECP2/X-inactivation status and phenotypic variability, we used this disease as a model to unveil the complex nature of a monogenic disorder. Whole exome sequencing was used to analyze the functional portion of the genome of two pairs of sisters with Rett syndrome. Although each pair of sisters had the same MECP2 (OMIM*300005) mutation and balanced X-inactivation, one individual from each pair could not speak or walk, and had a profound intellectual deficit (classical Rett syndrome), while the other individual could speak and walk, and had a moderate intellectual disability (Zappella variant). In addition to the MECP2 mutation, each patient has a group of variants predicted to impair protein function. The classical Rett girls, but not their milder affected sisters, have an enrichment of variants in genes related to oxidative stress, muscle impairment and intellectual disability and/or autism. On the other hand, a subgroup of variants related to modulation of immune system, exclusive to the Zappella Rett patients are driving toward a milder phenotype. We demonstrate that genome analysis has the potential to identify genetic modifiers of Rett syndrome, providing insight into disease pathophysiology. Combinations of mutations that affect speaking, walking and intellectual capabilities may represent targets for new therapeutic approaches. Most importantly, we demonstrated that monogenic diseases may be more complex than previously thought.     

De novo MECP2 duplication derived from paternal germ line result in dysmorphism and developmental delay

Xq28 duplications encompassing the methyl CpG binding protein 2 (MECP2) in males exhibit a distinct phenotype, including developmental delay, facial dysmorphism, muscular hypotonia, intellectual disability, poor or absent speech, recurrent infections and early death. The vast majority of affected males inherit the MECP2 duplication from their usually asymptomatic carrier mothers. Only a few cases with Xq28 duplication originating from de novo unbalanced X/Y translocation have been reported and the paternal origin of the aberration has only been validated in three males in the related literature. Here we present a karyotypically normal male with features characteristic of the MECP2 duplication syndrome. The genome-wide SNP genotyping shows a de novo 2.26-Mb duplication from Xq28 to the terminus. The genotypes of the SNPs within the duplicated region indicated a paternal origin. Furthermore, the results of fluorescence in situ hybridization (FISH) indicated a novel Xq:Yp translocation, characterized as der(Y)t(Y;X)(p11.32;q28), which suggests an aberrant that occurred during spermatogenesis. The phenotype is compared to the previously reported cases with Xq28 duplication originated from an unbalanced X/Y translocation, and there was no specific part of the phenotype that could be contributed to the origin of parental imbalances. This report further highlights the capacity of high-molecular cytogenetic methods, such as SNP array and FISH, in the identification of submicroscopic rearrangement, structural configuration and parental origin of aberrant while in the evaluation of children with idiopathic developmental delay and intellectual disability.     

The genetics of childhood obesity and interaction with dietary macronutrients

The genes contributing to childhood obesity are categorized into three different types based on distinct genetic and phenotypic characteristics. These types of childhood obesity are represented by rare monogenic forms of syndromic or non-syndromic childhood obesity, and common polygenic childhood obesity. In some cases, genetic susceptibility to these forms of childhood obesity may result from different variations of the same gene. Although the prevalence for rare monogenic forms of childhood obesity has not increased in recent times, the prevalence of common childhood obesity has increased in the United States and developing countries throughout the world during the past few decades. A number of recent genome-wide association studies and mouse model studies have established the identification of susceptibility genes contributing to common childhood obesity. Accumulating evidence suggests that this type of childhood obesity represents a complex metabolic disease resulting from an interaction with environmental factors, including dietary macronutrients. The objective of this article is to provide a review on the origins, mechanisms, and health consequences of obesity susceptibility genes and interaction with dietary macronutrients that predispose to childhood obesity. It is proposed that increased knowledge of these obesity susceptibility genes and interaction with dietary macronutrients will provide valuable insight for individual, family, and community preventative lifestyle intervention, and eventually targeted nutritional and medicinal therapies.     

A novel contiguous deletion involving $$\varvec{NDP},$$ MAOB and EFHC2 gene in a patient with familial Norrie disease: bilateral blindness and leucocoria without other deficits

Contiguous microdeletions of the Norrie disease pseudoglioma (NDP) region on chromosome Xp11.3 have been widely confirmed as contributing to the typical clinical features of Norrie disease (ND). However, the precise relation between genotype and phenotype could vary. The contiguous deletion of NDP and its neighbouring genes, MAOA/B and EFHC2, reportedly leads to syndromic clinical features such as microcephaly, intellectual disability, and epilepsy. Here we report a novel contiguous microdeletion of the NDP region containing the MAOB and EFHC2 genes, which causes eye defects but no cognitive disability. We detected a deletion of 494.6 kb at Xp11.3 in both the proband and carrier mother. This deletion was then used as the molecular marker in prenatal diagnosis for two subsequent pregnancies. The deletion was absent in one of the foetuses, who remain without any abnormalities at 2 years of age. The proband shows the typical ocular clinical features of ND including bilateral retinal detachment, microphthalmia, atrophic irides, corneal opacification, and cataracts, but no symptoms of microcephaly, intellectual disability, and epilepsy. This familial study demonstrates that a deficiency in one of two MAO genes may not lead to psychomotor delay, and deletion of EFHC2 may not cause epilepsy. Our observations provide new information on the genotype–phenotype relations of \({\textit{MAOA/B}}\) and EFHC2 genes involved in the contiguous deletions of ND.     

Genetically transitional disease: a new concept in genomic medicine

Traditional classification of genetic diseases as monogenic and polygenic has lagged far behind scientific progress. In this opinion article, we propose and define a new terminology, genetically transitional disease (GTD), referring to cases where a large-effect mutation is necessary, but not sufficient, to cause disease. This leads to a working disease nosology based on gradients of four types of genetic architecture: monogenic, polygenic, GTD, and mixed. We present four scenarios under which GTD may occur; namely, subsets of traditionally Mendelian disease, modifiable Tier 1 monogenic conditions, variable penetrance, and situations where a genetic mutational spectrum produces qualitatively divergent pathologies. The implications of the new nosology in precision medicine are discussed, in which therapeutic options may target the molecular cause or the disease phenotype.     

The genetics of human obesity

Obesity is an important cause of morbidity and mortality in developed countries, and is also becoming increasingly prevalent in the developing world. Although environmental factors are important, there is considerable evidence that genes also have a significant role in its pathogenesis. The identification of genes that are involved in monogenic, syndromic and polygenic obesity has greatly increased our knowledge of the mechanisms that underlie this condition. In the future, dissection of the complex genetic architecture of obesity will provide new avenues for treatment and prevention, and will increase our understanding of the regulation of energy balance in humans.     

Exome sequencing discloses <Emphasis Type="Italic">KALRN</Emphasis> homozygous variant as likely cause of intellectual disability and short stature in a consanguineous pedigree

Background

The recent availability of whole-exome sequencing has opened new possibilities for the evaluation of individuals with genetically undiagnosed intellectual disability.

Results

We report two affected siblings, offspring of first-cousin parents, with intellectual disability, hypotonia, short stature, growth hormone deficiency, and delayed bone age. All members of the nuclear family were genotyped, and exome sequencing was performed in one of the affected individuals. We used an in-house algorithm (CATCH v1.1) that combines homozygosity mapping with exome sequencing results and provides a list of candidate variants. One identified novel homozygous missense variant in KALRN (NM_003947.4:c.3644C>A: p.(Thr1215Lys)) was predicted to be pathogenic by all pathogenicity prediction software used (SIFT, PolyPhen, Mutation Taster). KALRN encodes the protein kalirin, which is a GTP-exchange factor protein with a reported role in cytoskeletal remodeling and dendritic spine formation in neurons. It is known that mice with ablation of Kalrn exhibit age-dependent functional deficits and behavioral phenotypes.

Conclusion

Exome sequencing provided initial evidence linking KALRN to monogenic intellectual disability in man, and we propose that KALRN is the causative gene for the autosomal recessive phenotype in this family.

     

Recurrent De Novo Mutations in PACS1 Cause Defective Cranial-Neural-Crest Migration and Define a Recognizable Intellectual-Disability Syndrome

We studied two unrelated boys with intellectual disability (ID) and a striking facial resemblance suggestive of a hitherto unappreciated syndrome. Exome sequencing in both families identified identical de novo mutations in PACS1, suggestive of causality. To support these genetic findings and to understand the pathomechanism of the mutation, we studied the protein in vitro and in vivo. Altered PACS1 forms cytoplasmic aggregates in vitro with concomitant increased protein stability and shows impaired binding to an isoform-specific variant of TRPV4, but not the full-length protein. Furthermore, consistent with the human pathology, expression of mutant PACS1 mRNA in zebrafish embryos induces craniofacial defects most likely in a dominant-negative fashion. This phenotype is driven by aberrant specification and migration of SOX10-positive cranial, but not enteric, neural-crest cells. Our findings suggest that PACS1 is necessary for the formation of craniofacial structures and that perturbation of its functions results in a specific syndromic ID phenotype.     

Sarcopenic Obesity Predicts Instrumental Activities of Daily Living Disability in the Elderly

Objective: To determine the association of sarcopenic obesity with the onset of Instrumental Activities of Daily Living (IADL) disability in a cohort of 451 elderly men and women followed for up to 8 years. Research Methods and Procedures: Sarcopenic obesity was defined at study baseline as appendicular skeletal muscle mass divided by stature squared <7.26 kg/m² in men and 5.45 kg/m² in women and percentage body fat greater than the 60th percentile of the study sample (28% body fat in men and 40% in women). Incident disability was defined as a loss of two or more points from baseline score on the IADL. Subjects with disability at baseline (scores < 8) were excluded. Cox proportional hazards analysis was used to determine the association of baseline sarcopenic obesity with onset of IADL disability, controlling for potential confounders. Results: Subjects with sarcopenic obesity at baseline were two to three times more likely to report onset of IADL disability during follow‐up than lean sarcopenic or nonsarcopenic obese subjects and those with normal body composition. The relative risk for incident disability in sarcopenic obese subjects was 2.63 (95% confidence interval, 1.19 to 5.85), adjusting for age, sex, physical activity level, length of follow‐up, and prevalent morbidity. Discussion: This is the first study, to our knowledge, to indicate that sarcopenic obesity is independently associated with and precedes the onset of IADL disability in the community‐dwelling elderly. The etiology of sarcopenic obesity is unknown but may include a combination of decreases in anabolic signals and obesity‐associated increases in catabolic signals in old age.     

Dosage Changes of a Segment at 17p13.1 Lead to Intellectual Disability and Microcephaly as a Result of Complex Genetic Interaction of Multiple Genes

The 17p13.1 microdeletion syndrome is a recently described genomic disorder with a core clinical phenotype of intellectual disability, poor to absent speech, dysmorphic features, and a constellation of more variable clinical features, most prominently microcephaly. We identified five subjects with copy-number variants (CNVs) on 17p13.1 for whom we performed detailed clinical and molecular studies. Breakpoint mapping and retrospective analysis of published cases refined the smallest region of overlap (SRO) for microcephaly to a genomic interval containing nine genes. Dissection of this phenotype in zebrafish embryos revealed a complex genetic architecture: dosage perturbation of four genes (ASGR1, ACADVL, DVL2, and GABARAP) impeded neurodevelopment and decreased dosage of the same loci caused a reduced mitotic index in vitro. Moreover, epistatic analyses in vivo showed that dosage perturbations of discrete gene pairings induce microcephaly. Taken together, these studies support a model in which concomitant dosage perturbation of multiple genes within the CNV drive the microcephaly and possibly other neurodevelopmental phenotypes associated with rearrangements in the 17p13.1 SRO.     

Molecular Diagnosis of Fragile X Syndrome in Subjects with Intellectual Disability of Unknown Origin: Implications of Its Prevalence in Regional Pakistan

Fragile-X syndrome (FXS) is the most common form of inherited intellectual disability (ID) and affects 0.7–3.0% of intellectually compromised population of unknown etiology worldwide. It is mostly caused by repeat expansion mutations in the FMR1 at chromosome Xq27.3. The present study aimed to develop molecular diagnostic tools for a better detection of FXS, to assess implementation of diagnostic protocols in a developing country and to estimate the prevalence of FXS in a cohort of intellectually disabled subjects from Pakistan. From a large pool of individuals with below normal IQ range, 395 subjects with intellectual disability of unknown etiology belonging to different regions of the country were recruited. Conventional-PCR, modified-PCR and Southern blot analysis methods were employed for the detection of CGG repeat polymorphisms in the FMR1 gene. Initial screening with conventional-PCR identified 13 suspected patients. Subsequent investigations through modified PCR and Southern blot analyses confirmed the presence of the FMR1 mutation, suggesting a prevalence of 3.5% and 2.8% (mean 3.3%) among the male and female ID patients, respectively. These diagnostic methods were further customized with the in-house conditions to offer robust screening of referral patients/families for diagnostics and genetic counseling. Prescreening and early diagnosis are crucial for designing a prudent strategy for the management of subjects with ID. Outcome of the study recommends health practitioners for implementation of molecular based FXS diagnosis in routine clinical practice to give a better care for patients similar to the ones included in the study.     

Comparative genetic analysis of different forms of low-renin arterial hypertension

Arterial hypertension (AH) ranks among the most widespread cardiovascular diseases and is clinically and genetically heterogeneous. Except for rare monogenic forms, AH is polygenic, and an important role in AH predisposition belongs to genes of the renin-angiotensin-aldosterone system. Low renin activity in blood plasma is observed in 20–25% of AH cases (low-renin form of AH), while aldosterone production can be elevated (hyperaldosteronism, HA) or normal in these cases. Several polymorphisms of the genes coding for the renin-angiotensin-aldosterone system components were studied in patients with low-renin AH forms: primary HA, idiopathic HA, and AH with a normal aldosterone level. The chimeric CYP11B2/CYP11B1 gene, causing monogenic familial HA type 1, was absent from all HA cases studied. The patient groups were compared with respect to the allele and genotype frequency distributions of the polymorphisms of several genes (CYP11B2 (C-344T), REN (C-5434T, C-5312T, and A BglI G), AGT (Thr174Met), ACE (I/D), CMA (G-1903A), AT2R1 (A1166C)), and their combinations. Analysis of the carriership of the allele and genotype combinations implicated CYP11B2, REN, ACE, CMA, and AT2R1 in low-renin HA. The results revealed both similar and different features in the genetic nature of different low-renin AH forms. Investigation of the genetic predisposition to clinically heterogeneous forms of polygenic diseases by comparing patient groups, formed in accordance with peculiarities of the disease course, holds much promise for understanding their hereditary background.     

X染色体连锁智力障碍遗传机制研究进展

x染色体连锁智力障碍（X-1inked intellectual disability,XUD）是一类位于x染色体上的基因发生突变引起的先天性智力障碍,所涉及的先天性智力障碍约占所有先天性智力障碍的15％。依据除了智力障碍外是否有其他生理方面的缺陷,XLID分为两类：S-XLID（syndromic forms）和NS．XLID（non-syndromic forms）。S-XLID表现在除了智力障碍外,还在新陈代谢方面、神经特征或者其他的体征——如骨骼、颅面部上有异常或者缺陷。该文对近年来XLID的致病机制研究进展作了部分阐述。     

Comparative evaluation of obesity-related parameters in junior sumo wrestlers and children with obesity

[Purpose]Exercise is a key factor in preventing obesity and metabolic syndrome. Sumo wrestlers increase their body size from childhood for athletic advantage; however, the risk of metabolic syndrome in junior sumo wrestlers is undetermined. Preventive measures against pediatric obesity should be initiated during childhood to prevent obesity in adulthood, considering its high global incidence. We comparatively evaluated the risk factors for metabolic syndrome in junior sumo wrestlers and children with obesity.[Methods]We enrolled 70 male children (age 9–17 years [sumo group, n = 14] and 9–14 years [other sports and non-exercise groups, n = 28 each]) and evaluated their anthropometric parameters (height, weight, body mass index z-score, obesity rate, waist circumference, waist to height ratio) and hematological parameters (total, low-density, high-density, and non-high-density lipoprotein-cholesterol; triglycerides; plasma glucose, and glycated hemoglobin levels).[Results]The BMI z-score, obesity rate, waist circumference (p < 0.05, along with the non-exercise group), and systolic blood pressure were significantly higher and the high-density cholesterol level was lower in the sumo group than in the other sports group (p < 0.05). The waist to height ratio was significantly higher in the non-exercise group than in the other sports group (p < 0.05). No significant difference was found in other blood lipid, plasma glucose (significantly lower level than the reference range in the sumo group, p < 0.05), and glycated hemoglobin (within the reference range in all groups) levels among the three groups.[Conclusion]Junior sumo wrestlers had a larger body size and higher blood pressure than children with obesity who exercised regularly. This provides direction for future research into targeted preventive interventions against metabolic syndrome for junior sumo wrestlers with large body size.