Molecular Genetic Cause Research Articles

Molecular genetic basis of Usher syndrome in the Czech population

SummaryA systematic literature search of the PubMed database (1 March 2016) using keywords ‘Usher syndrome’ AND ‘mutation’ AND ‘Czech Republic’ (or Belarus, Bulgaria, Estonia, Hungary, Latvia, Lithuania, Moldova, Poland, Slovakia, Romania, Russia, Ukraine) yielded 3 results. After inspection of retrieved abstracts we concluded that none of the published patients had an established molecular genetic cause of Usher syndrome. This is in striking contrast to numerous reports from Western European populations. In this presentation we will discuss our recently established program at a tertiary referral centre in Prague to genotype patients with Usher syndrome. So far 17 probands and 27 unaffected first degree relatives have been examined and donated DNA samples. The search into the molecular genetic causes is ongoing, however it is already apparent that there is an overrepresentation of the c.11864G>A; p.(Trp3955*) mutation in USH2A which was found on at least one allele in 9 probands (53%). The impact of our findings on clinical care and their potential to provide translational outcomes will be discussed. The spectrum of mutations identified in Czech Usher syndrome patients may also be relevant for neighbouring countries.

Two novel KERA mutations causing cornea plana in a Czech family and associated phenotypes

PurposeTo identify the molecular genetic cause in a previously not reported Czech family with the occurrence of cornea plana in two siblings.MethodsDetailed ophthalmological examination and direct sequencing of the KERA coding region in the proband followed by target analysis of the identified mutations in other family members.ResultsThe family was not aware of any consanguinity. Compound heterozygosity for a novel missense mutation c.209C>T; p.(Pro70Leu) and a novel splice site mutation c.887‐1G>A in KERA were detected in both affected individuals. The mother was a heterozygous carrier of c.887‐1G>A and the father of c.209C>T. In silico analysis supported the pathogenicity of both mutations. The younger brother, aged 13 years, had typical ocular phenotype of cornea plana with keratometry readings bellow 30 D, shallow anterior chamber, indistinct limbus and central corneal opacity. Corneal endothelial cell morphology was normal in the right eye; in the left eye specular microscopy images could not be taken. In the older brother, aged 20 years, marked thinning with protrusion in the superior part of the left cornea was present resulting into mean keratometry of 47.2 D. No corneal endothelial cell pathology was observed by specular microscopy bilaterally.ConclusionsThe identification of two novel heterozygous mutations in the second Czech family with cornea plana does not support the hypothesis of a founder effect. Marked corneal thinning and protrusion in cornea plana is a very rare finding and longitudinal follow‐up evaluation needs to be performed to determine its possible progressivity.

Analysis of FOXL2 detects three novel mutations and an atypical phenotype of blepharophimosis‐ptosis‐epicanthus inversus syndrome

Mutations in FOXL2 are known to cause autosomal dominant blepharophimosis-ptosis-epicanthus inversus syndrome (BPES), variably associated with premature ovarian failure. In this study, we report results of mutational screening in a Czech and Slovak patient population with BPES. Case series. Thirteen probands of Czech and one proband of Slovak origin with BPES and their available family members. Sanger sequencing and multiplex ligation-dependent probe amplification in 14 probands with BPES. Targeted mutational screening in first-degree relatives. Genetic characterization and phenotype evaluation in Czech and Slovak individuals with BPES and their family members. Eight different mutations were detected including three novel ones: c.5T>G; p.(Met2Arg), c.197C>A; p.(Ala66Glu) and c.701_702insTGCAGCCGCAGCGGCTGCAGCAGCTGCGGCTGCAGCCGC; p.(Ala222_Ala234dup). In one family, the molecular genetic cause of disease was not identified by the methodology used. In 13 pedigrees, a negative family history suggested a de novo origin, which could be confirmed by targeted mutational screening in four families. One 62-year-old female with the c.663_692dup30 mutation had an atypical phenotype presenting as moderate ptosis compensated by frontalis muscle contraction, no epicanthus inversus and no premature ovarian failure. The de novo mutation rate in FOXL2 is exceptionally high compared with other dominant disorders manifesting with an ocular phenotype. In cases reporting a negative family history, careful examination of both parents is important to exclude mild features of the BPES phenotype.

Early detection of bilateral cataracts in utero may represent a manifestation of severe congenital disease.

We observed bilateral cataracts on second trimester ultrasound, in two consecutive pregnancies, with no other structural defects detected. The parents were unrelated and had no family history for the disease. The first pregnancy was terminated in week 22. Copy number variation analysis revealed, in both the aborted fetus and the mother, a 495 kb duplication at 22q11.23 encompassing CRYBB3 and CRYBB2, and not present in variation databases. In the second pregnancy, lens hyperechogenicity was detected by ultrasound at week 13 and 4 days. The identical duplication at 22q11.23 was found in the fetus and considered as possibly pathogenic. At weeks 22 and 30, smaller orbit measurements were elucidated on ultrasound, raising concerns as to the underlying molecular genetic cause, necessitating further investigation. Whole-exome sequencing, using DNA of the first fetus, was performed shortly after the birth of a male child, and two truncating RAB3GAP1 mutations were detected: c.538G>T; p. (Glu180*) and c.943C>T; p. (Arg315*). Neither mutation has been previously reported to be disease-causing; however, evaluation in the context of previously published literature indicated their deleterious nature, implying a clinical diagnosis of Warburg micro syndrome or Martsolf syndrome. Sanger sequencing confirmed segregation of the two mutations within the family, consistent with autosomal recessive inheritance. The child born from the second pregnancy showed features typical of Warburg micro syndrome, with the exception of microcephaly, at age 31 months. © 2016 Wiley Periodicals, Inc.

Australian Cattle Dogs with Neuronal Ceroid Lipofuscinosis are Homozygous for a CLN5 Nonsense Mutation Previously Identified in Border Collies.

BackgroundNeuronal ceroid lipofuscinosis (NCL), a fatal neurodegenerative disease, has been diagnosed in young adult Australian Cattle Dogs.ObjectiveCharacterize the Australian Cattle Dog form of NCL and determine its molecular genetic cause.AnimalsTissues from 4 Australian Cattle Dogs with NCL‐like signs and buccal swabs from both parents of a fifth affected breed member. Archived DNA samples from 712 individual dogs were genotyped.MethodsTissues were examined by fluorescence, electron, and immunohistochemical microscopy. A whole‐genome sequence was generated for 1 affected dog. A TaqMan allelic discrimination assay was used for genotyping.ResultsThe accumulation of autofluorescent cytoplasmic storage material with characteristic ultrastructure in tissues from the 4 affected dogs supported a diagnosis of NCL. The whole‐genome sequence contained a homozygous nonsense mutation: CLN5:c.619C>T. All 4 DNA samples from clinically affected dogs tested homozygous for the variant allele. Both parents of the fifth affected dog were heterozygotes. Archived DNA samples from 346 Australian Cattle Dogs, 188 Border Collies, and 177 dogs of other breeds were homozygous for the reference allele. One archived Australian Cattle Dog sample was from a heterozygote.Conclusions and Clinical ImportanceThe homozygous CLN5 nonsense is almost certainly causal because the same mutation previously had been reported to cause a similar form of NCL in Border Collies. Identification of the molecular genetic cause of Australian Cattle Dog NCL will allow the use of DNA tests to confirm the diagnosis of NCL in this breed.

The Holstein Friesian Lethal Haplotype 5 (HH5) Results from a Complete Deletion of TBF1M and Cholesterol Deficiency (CDH) from an ERV-(LTR) Insertion into the Coding Region of APOB

BackgroundWith the availability of massive SNP data for several economically important cattle breeds, haplotype tests have been performed to identify unknown recessive disorders. A number of so-called lethal haplotypes, have been uncovered in Holstein Friesian cattle and, for at least seven of these, the causative mutations have been identified in candidate genes. However, several lethal haplotypes still remain elusive. Here we report the molecular genetic causes of lethal haplotype 5 (HH5) and cholesterol deficiency (CDH). A targeted enrichment for the known genomic regions, followed by massive parallel sequencing was used to interrogate for causative mutations in a case/control approach.MethodsTargeted enrichment for the known genomic regions, followed by massive parallel sequencing was used in a case/control approach. PCRs for the causing mutations were developed and compared to routine imputing in 2,100 (HH5) and 3,100 (CDH) cattle.ResultsHH5 is caused by a deletion of 138kbp, spanning position 93,233kb to 93,371kb on chromosome 9 (BTA9), harboring only dimethyl-adenosine transferase 1 (TFB1M). The deletion breakpoints are flanked by bovine long interspersed nuclear elements Bov-B (upstream) and L1ME3 (downstream), suggesting a homologous recombination/deletion event. TFB1M di-methylates adenine residues in the hairpin loop at the 3’-end of mitochondrial 12S rRNA, being essential for synthesis and function of the small ribosomal subunit of mitochondria. Homozygous TFB1M-/- mice reportedly exhibit embryonal lethality with developmental defects. A 2.8% allelic frequency was determined for the German HF population. CDH results from a 1.3kbp insertion of an endogenous retrovirus (ERV2-1-LTR_BT) into exon 5 of the APOB gene at BTA11:77,959kb. The insertion is flanked by 6bp target site duplications as described for insertions mediated by retroviral integrases. A premature stop codon in the open reading frame of APOB is generated, resulting in a truncation of the protein to a length of only <140 amino acids. Such early truncations have been shown to cause an inability of chylomicron excretion from intestinal cells, resulting in malabsorption of cholesterol. The allelic frequency of this mutation in the German HF population was 6.7%, which is substantially higher than reported so far. Compared to PCR assays inferring the genetic variants directly, the routine imputing used so far showed a diagnostic sensitivity of as low as 91% (HH5) and 88% (CDH), with a high specificity for both (≥99.7%).ConclusionWith the availability of direct genetic tests it will now be possible to more effectively reduce the carrier frequency and ultimately eliminate the disorders from the HF populations. Beside this, the fact that repetitive genomic elements (RE) are involved in both diseases, underline the evolutionary importance of RE, which can be detrimental as here, but also advantageous over generations.

Phenotypic features of CRB1-associated early-onset severe retinal dystrophy and the different molecular approaches to identifying the disease-causing variants.

The aim of this study was to determine the molecular genetic basis of an early-onset severe retinal dystrophy in three unrelated consecutive patients of Czech origin and to describe their ocular phenotype. DNA samples from two probands were analyzed using a genotyping microarray (Asper) followed by either target analysis of 43 genes implicated in retinal disorders by next generation sequencing or whole-exome sequencing, respectively. The third proband underwent conventional Sanger sequencing of CRB1 based on her ocular findings. All three probands harboured a known disease-causing mutation c.2843G>A; p.(Cys948Tyr) in the CRB1 gene. One individual was homozygous for this mutation, while in the other two probands c.2308G>A; p.(Gly770Ser) and c.3121A>G; p.(Met1041Val) were also identified in the heterozygous state, respectively. Both variants were novel and evaluated by in silico analysis as pathogenic. A false-negative result was observed in one of the two samples examined by the genotyping microarray. Disease onset in all patients was before the age of 7years. Hypermetropic refractive error, bilateral nummular retinal pigmentation, retinal thickening and cystoid spaces in the macula were observed in two probands, aged 6 and 7years. The third proband, aged 28years, had bone spicule-like pigmentary changes associated with increased retinal nerve fiber layer. The first study reporting on the molecular genetic cause of non-syndromic early-onset severe retinal dystrophy in Czech patients identified one homozygous and two compound heterozygote probands with CRB1 mutations. Retina nerve fibre layer measurements should be considered an integral part of the clinical evaluation of retinal dystrophies. Detailed clinical examination and imaging can both direct molecular screening and help to confirm or refute disease causation of identified variants.

Un caso de escorbuto en un joven del siglo XXI

Coenzyme Q10 (CoQ10) is an important component of the mitochondrial respiratory chain (RC) and is critical for energy production. Although the prevalence of CoQ10 deficiency is still unknown, the general consensus is that the condition is under-diagnosed. The aim of this study was to retrospectively investigate CoQ10 deficiency in frozen muscle specimens in a cohort of ethnically diverse patients who received muscle biopsies for the investigation of a possible RC deficiency (RCD).Muscle samples were homogenized whereby 600 ×g supernatants were used to analyze RC enzyme activities, followed by quantification of CoQ10 by stable isotope dilution liquid chromatography tandem mass spectrometry. The experimental group consisted of 156 patients of which 76 had enzymatically confirmed RCDs. To further assist in the diagnosis of CoQ10 deficiency in this cohort, we included sequencing of 18 selected nuclear genes involved with CoQ10 biogenesis in 26 patients with low CoQ10 concentration in muscle samples.Central 95% reference intervals (RI) were established for CoQ10 normalized to citrate synthase (CS) or protein. Nine patients were considered CoQ10 deficient when expressed against CS, while 12 were considered deficient when expressed against protein. In two of these patients the molecular genetic cause could be confirmed, of which one would not have been identified as CoQ10 deficient if expressed only against protein content.In this retrospective study, we report a central 95% reference interval for 600 ×g muscle supernatants prepared from frozen samples. The study reiterates the importance of including CoQ10 quantification as part of a diagnostic approach to study mitochondrial disease as it may complement respiratory chain enzyme assays with the possible identification of patients that may benefit from CoQ10 supplementation. However, the anomaly that only a few patients were identified as CoQ10 deficient against both markers (CS and protein), while the majority of patients where only CoQ10 deficient against one of the markers (and not the other), remains problematic. We therefore conclude from our data that, to prevent possibly not diagnosing a potential CoQ10 deficiency, the expression of CoQ10 levels in muscle on both CS as well as protein content should be considered.

Identification of a novel BCKDHA deletion causing maple syrup urine disease

Maple syrup urine disease (MSUD) is a rare autosomal recessive disorder of the catabolism of branched-chain amino acids. The disorder can be caused by mutations within any of the BCKDHA, BCKDHB, DBT and DLD genes encoding the branched-chain alpha-ketoacid dehydrogenase complex. The aim of the study was to identify the molecular genetic cause of classic MSUD in a male neonate reported by newborn screening on the fourth day of life. The genetic analyses involved polymerase chain reaction (PCR) and sequencing of the BCKDHA, BCKDHB, and DBT genes. The results showed that the patient was homozygous for a novel 3021 bp deletion within the BCKDHA gene including exon 4 (NG_013004.1:g.13869_16889del) of this gene. The lack of exon 4 causes a reading frame shift and a premature termination codon in BCKDHA exon 5 (NP_000700.1:p.Gly126ValfsTer3). This strongly suggests that the novel BCKDHA deletion is pathogenic and is the cause of classic MSUD in this patient.

Polymorphism of the LCT gene regulatory region in Turkicspeaking populations of the Altay-Sayan region (southern Siberia)

Retention of lactase activity in adulthood (lactase persistence) is one of the most important adaptive traits for human populations that consume fresh milk from domestic animals. At a molecular-genetic level, lactase persistence is determined by the presence of specific alleles of polymorphic sites in cis-regulatory elements of the LCT gene located on chromosome 2q21. Ascertainment of the molecular-genetic causes of lactase persistence has made this trait one of the most convenient for studying mechanisms of human population adaptation to environmental conditions. But the populations of many regions remain insufficiently investigated in relation to the genetic variability of the LCT loci. This paper presents the results of polymorphism analysis of loci, including the enhancer element for the LCT gene and its flanking regions, in two Turkic-speaking populations from southern Siberia, Altaian Kazakhs and Khakasses. It was found that the “European” allele LCT-13910T is the most characteristic of the Turkic-speaking populations from Altai-Sayan regions among all the polymorphic variants associated with lactase persistence. The expansion of the “European” allele LCT-13910T to the gene pool of the populations in southern Siberia could be related to migration waves of ancient herders form western Eurasia during the Bronze Age (in III – II millennium BC). A decrease of the LCT-13910T allele frequency and the total frequency of its carriers in the Turkic-speaking populations of southern Siberia in comparison with the majority of European populations and the Kazakhs from southern Central Asia can be attributed to: (1) a significant influence on the Altai- Sayan population’s gene pool by Eastern Eurasian populations, for which the LCT-13910T allele is rare; (2) a lesser adaptive significance of lactase persistence for south Siberian populations, compared to the populations of Europe. Rare and unique SNPs in the locus under consideration that were found in the Altaian Kazakhs (LCT-13895G &gt; C and LCT-13927C &gt; G) and Khakasses (LCT-14011C &gt; T) potentially play a role in regulation of LCT gene expression, because they are located within the enhancer, regulating activity of its promoter.

Quantitative autism symptom patterns recapitulate differential mechanisms of genetic transmission in single and multiple incidence families.

BackgroundPrevious studies have demonstrated aggregation of autistic traits in undiagnosed family members of children with autism spectrum disorder (ASD), which has significant implications for ASD risk in their offspring. This study capitalizes upon a large, quantitatively characterized clinical-epidemiologic family sample to establish the extent to which family transmission pattern and sex modulate ASD trait aggregation.MethodsData were analyzed from 5515 siblings (2657 non-ASD and 2858 ASD) included in the Interactive Autism Network. Autism symptom levels were measured using the Social Responsiveness Scale (SRS) and by computing Diagnostic and Statistical Manual of Mental Disorders—Fifth Edition (DSM-5) symptom scores based on items from the SRS and Social Communication Questionnaire. Generalized estimating equation models evaluated the influence of family incidence types (single versus multiple incidence families; male-only ASD-affected families versus families with female ASD-affected children), diagnostic group (non-ASD children with and without a history of language delay with autistic speech and ASD-affected children), and sibling sex on ASD symptom levels.ResultsNon-ASD children manifested elevated ASD symptom burden when they were members of multiple incidence families—this effect was accentuated for male children in female ASD-containing families—or when they had a history of language delay with autistic qualities of speech. In this sample, ASD-affected children from multiple incidence families had lower symptom levels than their counterparts in single incidence families. Recurrence risk for ASD was higher for children from female ASD-containing families than for children from male-only families.ConclusionsSex and patterns of family transmission modulate the risk of autism symptom burden in undiagnosed siblings of ASD-affected children. Identification of these symptoms/traits and their molecular genetic causes may have significant implications for genetic counseling and for understanding inherited liabilities that confer risk for ASD in successive generations. Autism symptom elevations were more dramatic in non-ASD children from multiple incidence families and those with a history of language delay and autistic qualities of speech, identifying sub-groups at substantially greater transmission risk. Higher symptom burden and greater recurrence in children from female ASD-containing families indicate that familial aggregation patterns are further qualified by sex-specific thresholds, supportive of the notion that females require a higher burden of deleterious liability to cross into categorical ASD diagnosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-015-0050-z) contains supplementary material, which is available to authorized users.

Understanding the molecular genetic causes of inherited corneal disorders

SummaryInherited corneal diseases comprise a group of clinically and genetically heterogeneous disorders that can lead to bilateral severely impaired vision and/or blindness. Advances in next generation sequencing (NGS) technologies have revolutionised clinical genetics over the past five years. The application of NGS, in combination with genome wide association studies, to the field of inherited corneal disorders has provided significant insights into the genetics of corneal diseases and their underlying aetiology. An overview of our current understanding of the genetics of monogenic corneal dystrophies, as well as the contribution of genetic factors to complex conditions such as keratoconus and Fuchs endothelial corneal dystrophy (FECD), will be provided. Examples from our laboratory exploiting NGS platforms, in combination with careful phenotyping of patient sub‐groups, to identify novel genetic causes and mechanisms of inherited corneal disorders such as; posterior polymorphous corneal dystrophy, epithelial recurrent erosion dystrophy, and X‐linked megalocornea, will be highlighted. Furthermore the impact of these findings on clinical care and their potential to provide translational outcomes will be discussed.

Whole exome sequencing in patients with congenital cataracts

SummaryNext‐generation sequencing (NGS) represents one of the most significant technological advances in the biological sciences of the past decade. NGS is now being introduced by many laboratories for routine diagnostic use. For genetically heterogeneous disorders approaches include custom‐designed target enrichment permitting analysis of disease‐associated gene panels and whole exome sequencing (WES). The sensitivity, speed and cost per sample makes WES a valuable tool and it is increasingly being used to identify the molecular genetic causes of inherited cataracts. The detection rate of disease‐causing mutations is high and the results enhance clinical diagnosis and genetic counselling of the affected families.

Exome sequencing reveals novel and recurrent mutations with clinical significance in inherited retinal dystrophies.

This study aimed to identify the underlying molecular genetic cause in four Spanish families clinically diagnosed of Retinitis Pigmentosa (RP), comprising one autosomal dominant RP (adRP), two autosomal recessive RP (arRP) and one with two possible modes of inheritance: arRP or X-Linked RP (XLRP). We performed whole exome sequencing (WES) using NimbleGen SeqCap EZ Exome V3 sample preparation kit and SOLID 5500xl platform. All variants passing filter criteria were validated by Sanger sequencing to confirm familial segregation and the absence in local control population. This strategy allowed the detection of: (i) one novel heterozygous splice-site deletion in RHO, c.937-2_944del, (ii) one rare homozygous mutation in C2orf71, c.1795T>C; p.Cys599Arg, not previously associated with the disease, (iii) two heterozygous null mutations in ABCA4, c.2041C>T; p.R681* and c.6088C>T; p.R2030*, and (iv) one mutation, c.2405-2406delAG; p.Glu802Glyfs*31 in the ORF15 of RPGR. The molecular findings for RHO and C2orf71 confirmed the initial diagnosis of adRP and arRP, respectively, while patients with the two ABCA4 mutations, both previously associated with Stargardt disease, presented symptoms of RP with early macular involvement. Finally, the X-Linked inheritance was confirmed for the family with the RPGR mutation. This latter finding allowed the inclusion of carrier sisters in our preimplantational genetic diagnosis program.

Macular corneal dystrophy and associated corneal thinning.

To identify the molecular genetic cause of macular corneal dystrophy (MCD) in four probands, and characterize phenotypic similarities between MCD and keratoconus. We performed ophthalmological examination, Scheimpflug imaging (Pentacam, Oculus Inc.), histopathological examination of excised corneal buttons, and direct sequencing of the CHST6 coding region. Pentacam measurements were taken in six eyes of three probands. All showed diffuse corneal thinning with paracentral steepening of the anterior corneal surface that was graded as keratoconus by the integrated software, but without associated ectasia of the posterior corneal surface or regional thinning. Homozygous or compound heterozygous CHST6 mutations were identified in all cases, including two novel mutations, c.13C>T; p.(Arg5Cys) and c.289C>T; p.(Arg97Cys). Localized elevation of the anterior corneal curvature can occur in MCD in the absence of other features of keratoconus. The identification of a further two Czech probands with the compound allele c.[484C>G; 599T>G] supports the enrichment of this allele in the study population.

Genetics of congenital hypogonadotropic hypogonadism in Denmark

Congenital hypogonadotropic hypogonadism (CHH) is a rare disorder characterized by incomplete/absent puberty caused by deficiency or defective action of gonadotropin-releasing hormone (GnRH). The phenotypic features of patients with CHH vary from genital hypoplasia and absent puberty to reversal of HH later in life. We examined the genetics and clinical features of CHH in Denmark. Forty-one male patients were screened for mutations in KAL1, FGFR1, FGF8, PROK2, PROKR2, GNRHR, TAC3, TACR3, and KISS1R. CHD7 was screened in two patients with hearing loss. In 12 patients, a molecular genetic cause for CHH was found. Four patients had mutations in KAL1 (C105VfsX13, C53X, ex5-8del, R257X), and five in FGFR1 (G97S, R209C, A512V, R646W, and c.1614C>T, (p.I538I), predicted to affect splicing). All 9 had severe HH (cryptorchidism and/or micropenis), and 2 had cleft lip/palate. One patient with a previously reported homozygous R262Q mutation in GNRHR displayed fascinating temporal variation in his phenotype. Two patients with hearing loss had CHD7 mutations (c.7832_7841del (p.K2611MfsX25) and c.2443-2A>C), confirming that CHH patients with CHARGE syndrome-associated features should be screened for mutations in CHD7.

Osteogenesis imperfecta: Clinical diagnosis, nomenclature and severity assessment

Recently, the genetic heterogeneity in osteogenesis imperfecta (OI), proposed in 1979 by Sillence et al., has been confirmed with molecular genetic studies. At present, 17 genetic causes of OI and closely related disorders have been identified and it is expected that more will follow. Unlike most reviews that have been published in the last decade on the genetic causes and biochemical processes leading to OI, this review focuses on the clinical classification of OI and elaborates on the newly proposed OI classification from 2010, which returned to a descriptive and numerical grouping of five OI syndromic groups. The new OI nomenclature and the pre-and postnatal severity assessment introduced in this review, emphasize the importance of phenotyping in order to diagnose, classify, and assess severity of OI. This will provide patients and their families with insight into the probable course of the disorder and it will allow physicians to evaluate the effect of therapy. A careful clinical description in combination with knowledge of the specific molecular genetic cause is the starting point for development and assessment of therapy in patients with heritable disorders including OI. © 2014 The Authors. American Journal of Medical Genetics Published by Wiley Periodicals, Inc. This is an open access article under the terms of the Creative Commons Attribution–NonCommercial–NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Y-chromosome microdeletions are not associated with SHOX haploinsufficiency

studyquestion: Are Y-chromosome microdeletions associated with SHOX haploinsufficiency, thus representing a risk of skeletal anom- alies for the carriers and their male descendents? summaryanswer: The present study shows that SHOX haploinsufficiency is unlikely to be associated with Y-chromosome microdele- tions. what is known already: Y-chromosome microdeletions are not commonly known as a major molecular genetic cause of any patho- logical condition except spermatogenic failure. However, it has been recently proposed that they are associated not only with infertility but also with anomalies in the pseudoautosomal regions (PAR), among which SHOX haploinsufficiency stands out with a frequency of 5.4% in microdele- tion carriers bearing a normal karyotype. This finding implies that sons fathered by men with Y-chromosome defects will not only exhibit fertility problems, but might also suffer from SHOX-related conditions. study design: Five European laboratories (Florence, Munster, Barcelona, Padova and Ancona), routinely performing Y-chromosome microdeletion screening, were enrolled in a multicenter study. participants/materials, setting, methods: PAR-linked and SHOX copy number variations (CNVs) were analyzed in 224 patients carrying Y-chromosome microdeletions and 112 controls with an intact Y chromosome, using customized X-chromosome-specific array-CGH platforms and/or qPCR assays for SHOX and SRY genes. main results and the role of chance: Our data show that 220 out of 224 (98.2%) microdeletion carriers had a normal SHOX copy number, as did all the controls. No SHOX deletions were found in any of the examined subjects (patients as well as controls), thus excluding an association with SHOX haploinsufficiency. SHOX duplications were detected in 1.78% of patients (n ¼ 4), of whom two had an abnormal and two a normal karyotype. This might suggest that Y-chromosome microdeletions have a higher incidence for SHOX duplications, irrespective of the patient's karyotype. However, the only clinical condition observed in our four SHOX-duplicated patients was infertility. limitations, reasons for caution: The number of controls analyzed is rather low to assess whether the SHOX duplications found in the two men with Y-chromosome microdeletions and a normal karyotype represent a neutral polymorphism or are actually associated with the presence of the microdeletion. wider implications of the findings: Men suffering from infertility due to the presence of Y-chromosome microdeletions can resort to artificial reproductive technology (ART) to father their biological children. However, infertile couples must be aware of the risks implied and this makes genetic counseling a crucial step in the patient's management. This study does not confirm previous alarming data that showed an association between Y-chromosome microdeletions and SHOX haploinsufficiency. Our results imply that deletion carriers have no augmented

Identification of Mutations Causing Inherited Retinal Degenerations in the Israeli and Palestinian Populations Using Homozygosity Mapping

The Israeli and Palestinian populations are known to have a relatively high level of consanguineous marriages, leading to a relatively high frequency of autosomal recessive (AR) diseases. Our purpose was to use the homozygosity mapping approach, aiming to prioritize the set of genes and identify the molecular genetic causes underlying AR retinal degenerations in the Israeli and Palestinian populations. Clinical analysis included family history, ocular examination, full-field electroretinography (ERG), and funduscopy. Molecular analysis included homozygosity mapping and mutation analysis of candidate genes. We recruited for the study families with AR nonsyndromic retinal degenerations, including mainly retinitis pigmentosa (RP), cone-rod degeneration (CRD), and Leber congenital amaurosis (LCA). With the aim to identify the causative genes in these families, we performed homozygosity mapping using whole genome single nucleotide polymorphism (SNP) arrays in 125 families. The analysis revealed the identification of 14 mutations, 5 of which are novel, in 16 of the families. The mutations were identified in the following eight genes: RDH12, PROM1, MFRP, TULP1, LCA5, CEP290, NR2E3, and EYS. While most patients had a retinal disease that is compatible with the causing gene, in some cases new clinical features are evident. Homozygosity mapping is a powerful tool to identify genetic defects underlying heterogeneous AR disorders, such as RP and LCA, in consanguineous and nonconsanguineous patients. The identification of significant and large homozygous regions, which do not include any known retinal disease genes, may be a useful tool to identify novel disease-causing genes, using next generation sequencing.

Recent Developments in Cardiovascular Genetics

Recent Developments in Cardiovascular Genetics