Bi-allelic ACBD6 variants lead to a neurodevelopmental syndrome with progressive and complex movement disorders

The acyl-CoA-binding domain-containing protein 6 (ACBD6) is ubiquitously expressed, plays a role in the acylation of lipids and proteins and regulates the N-myristoylation of proteins via N-myristoyltransferase enzymes (NMTs). However, its precise function in cells is still unclear, as is the consequence of ACBD6 defects on human pathophysiology. Using exome sequencing and extensive international data sharing efforts, we identified 45 affected individuals from 28 unrelated families (consanguinity 93%) with bi-allelic pathogenic, predominantly loss-of-function (18/20) variants in ACBD6. We generated zebrafish and Xenopus tropicalis acbd6 knockouts by CRISPR/Cas9 and characterized the role of ACBD6 on protein N-myristoylation with myristic acid alkyne (YnMyr) chemical proteomics in the model organisms and human cells, with the latter also being subjected further to ACBD6 peroxisomal localization studies. The affected individuals (23 males and 22 females), aged 1-50 years, typically present with a complex and progressive disease involving moderate-to-severe global developmental delay/intellectual disability (100%) with significant expressive language impairment (98%), movement disorders (97%), facial dysmorphism (95%) and mild cerebellar ataxia (85%) associated with gait impairment (94%), limb spasticity/hypertonia (76%), oculomotor (71%) and behavioural abnormalities (65%), overweight (59%), microcephaly (39%) and epilepsy (33%). The most conspicuous and common movement disorder was dystonia (94%), frequently leading to early-onset progressive postural deformities (97%), limb dystonia (55%) and cervical dystonia (31%). A jerky tremor in the upper limbs (63%), a mild head tremor (59%), parkinsonism/hypokinesia developing with advancing age (32%) and simple motor and vocal tics were among other frequent movement disorders. Midline brain malformations including corpus callosum abnormalities (70%), hypoplasia/agenesis of the anterior commissure (66%), short midbrain and small inferior cerebellar vermis (38% each) as well as hypertrophy of the clava (24%) were common neuroimaging findings. Acbd6-deficient zebrafish and Xenopus models effectively recapitulated many clinical phenotypes reported in patients including movement disorders, progressive neuromotor impairment, seizures, microcephaly, craniofacial dysmorphism and midbrain defects accompanied by developmental delay with increased mortality over time. Unlike ACBD5, ACBD6 did not show a peroxisomal localization and ACBD6-deficiency was not associated with altered peroxisomal parameters in patient fibroblasts. Significant differences in YnMyr-labelling were observed for 68 co- and 18 post-translationally N-myristoylated proteins in patient-derived fibroblasts. N-myristoylation was similarly affected in acbd6-deficient zebrafish and X. tropicalis models, including Fus, Marcks and Chchd-related proteins implicated in neurological diseases. The present study provides evidence that bi-allelic pathogenic variants in ACBD6 lead to a distinct neurodevelopmental syndrome accompanied by complex and progressive cognitive and movement disorders.

The recurrent deep intronic pseudoexon-inducing variant COL6A1 c.930+189C>T results in a consistently severe phenotype of COL6-related dystrophy: Towards clinical trial readiness for splice-modulating therapy

Collagen VI-related dystrophies (COL6-RDs) manifest with a spectrum of clinical phenotypes, ranging from Ullrich congenital muscular dystrophy (UCMD), presenting with prominent congenital symptoms and characterised by progressive muscle weakness, joint contractures and respiratory insufficiency, to Bethlem muscular dystrophy, with milder symptoms typically recognised later and at times resembling a limb girdle muscular dystrophy, and intermediate phenotypes falling between UCMD and Bethlem muscular dystrophy. Despite clinical and immunohistochemical features highly suggestive of COL6-RD, some patients had remained without an identified causative variant in COL6A1, COL6A2 or COL6A3. With combined muscle RNA-sequencing and whole-genome sequencing we uncovered a recurrent, de novo deep intronic variant in intron 11 of COL6A1 (c.930+189C>T) that leads to a dominantly acting in-frame pseudoexon insertion. We subsequently identified and have characterised an international cohort of forty-four patients with this COL6A1 intron 11 causative variant, one of the most common recurrent causative variants in the collagen VI genes. Patients manifest a consistently severe phenotype characterised by a paucity of early symptoms followed by an accelerated progression to a severe form of UCMD, except for one patient with somatic mosaicism for this COL6A1 intron 11 variant who manifests a milder phenotype consistent with Bethlem muscular dystrophy. Characterisation of this individual provides a robust validation for the development of our pseudoexon skipping therapy. We have previously shown that splice-modulating antisense oligomers applied in vitro effectively decreased the abundance of the mutant pseudoexon-containing COL6A1 transcripts to levels comparable to the in vivo scenario of the somatic mosaicism shown here, indicating that this therapeutic approach carries significant translational promise for ameliorating the severe form of UCMD caused by this common recurrent COL6A1 causative variant to a Bethlem muscular dystrophy phenotype.

National Rapid Genome Sequencing in Neonatal Intensive Care

Importance

National implementation of rapid trio genome sequencing (rtGS) in a clinical acute setting is essential to ensure advanced and equitable care for ill neonates.

Objective

To evaluate the feasibility, diagnostic efficacy, and clinical utility of rtGS in neonatal intensive care units (NICUs) throughout Israel.

Design, Setting, and Participants

This prospective, public health care-based, multicenter cohort study was conducted from October 2021 to December 2022 with the Community Genetics Department of the Israeli Ministry of Health and all Israeli medical genetics institutes (n = 18) and NICUs (n = 25). Critically ill neonates suspected of having a genetic etiology were offered rtGS. All sequencing, analysis, and interpretation of data were performed in a central genomics center at Tel-Aviv Sourasky Medical Center. Rapid results were expected within 10 days. A secondary analysis report, issued within 60 days, focused mainly on cases with negative rapid results and actionable secondary findings. Pathogenic, likely pathogenic, and highly suspected variants of unknown significance (VUS) were reported.

Main Outcomes and Measures

Diagnostic rate, including highly suspected disease-causing VUS, and turnaround time for rapid results. Clinical utility was assessed via questionnaires circulated to treating neonatologists.

Results

A total of 130 neonates across Israel (70 [54%] male; 60 [46%] female) met inclusion criteria and were recruited. Mean (SD) age at enrollment was 12 (13) days. Mean (SD) turnaround time for rapid report was 7 (3) days. Diagnostic efficacy was 50% (65 of 130) for disease-causing variants, 11% (14 of 130) for VUS suspected to be causative, and 1 novel gene candidate (1%). Disease-causing variants included 12 chromosomal and 52 monogenic disorders as well as 1 neonate with uniparental disomy. Overall, the response rate for clinical utility questionnaires was 82% (107 of 130). Among respondents, genomic testing led to a change in medical management for 24 neonates (22%). Results led to immediate precision medicine for 6 of 65 diagnosed infants (9%), an additional 2 (3%) received palliative care, and 2 (3%) were transferred to nursing homes.

Conclusions and Relevance

In this national cohort study, rtGS in critically ill neonates was feasible and diagnostically beneficial in a public health care setting. This study is a prerequisite for implementation of rtGS for ill neonates into routine care and may aid in design of similar studies in other public health care systems.

Relationships between Circulating Biomarkers and Body Composition Parameters in Patients with Metabolic Syndrome: A Community-Based Study

Metabolic syndrome (MetS) is a complex disease involving multiple physiological, biochemical, and metabolic abnormalities. The search for reliable biomarkers may help to better elucidate its pathogenesis and develop new preventive and therapeutic strategies. In the present population-based study, we looked for biomarkers of MetS among obesity- and inflammation-related circulating factors and body composition parameters in 1079 individuals (with age range between 18 and 80) belonging to an ethnically homogeneous population. Plasma levels of soluble markers were measured by using ELISA. Body composition parameters were assessed using bioimpedance analysis (BIA). Statistical analysis, including mixed-effects regression, with MetS as a dependent variable, revealed that the most significant independent variables were mainly adipose tissue-related phenotypes, including fat mass/weight (FM/WT) [OR (95% CI)], 2.77 (2.01-3.81); leptin/adiponectin ratio (L/A ratio), 1.50 (1.23-1.83); growth and differentiation factor 15 (GDF-15) levels, 1.32 (1.08-1.62); inflammatory markers, specifically monocyte to high-density lipoprotein cholesterol ratio (MHR), 2.53 (2.00-3.15), and a few others. Additive Bayesian network modeling suggests that age, sex, MHR, and FM/WT are directly associated with MetS and probably affect its manifestation. Additionally, MetS may be causing the GDF-15 and L/A ratio. Our novel findings suggest the existence of complex, age-related, and possibly hierarchical relationships between MetS and factors associated with obesity.

Elevated circulating levels of IL-34 are strongly associated with osteoporosis

In this cross-sectional study, we observed a strong, age-independent association of circulating interleukin-34 (IL-34) levels with osteoporosis.

PURPOSE

The reported capacity of IL-34 to induce and enhance osteoclastogenesis suggests its potential involvement in the pathogenesis of osteoporosis. Our study aimed to evaluate whether there is an association between IL-34 expression and osteoporosis.

METHODS

We enrolled 30 women with osteoporosis and 230 age-matched non-osteoporotic women as a control group. Osteoporosis diagnosis was based on dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femoral neck. Body composition parameters were assessed by the bioimpedance method. Plasma IL-34 levels were measured by ELISA.

RESULTS

In comparison with the control group, the mean plasma IL-34 levels were significantly higher in osteoporotic women (164.61 ± 36.40 pg/ml vs. 665.43 ± 253.67 pg/ml, p = 0.0002), whereas basal metabolic rate (BMR) was significantly lower (1422.03 ± 6.80 kcal vs. 1339.39 ± 17.52 kcal, p = 0.00007). Both variables remained statistically significant after adjustment for age (p < 0.001). We did not observe correlations between plasma IL-34 levels and body composition parameters in osteoporotic and control groups. Multiple logistic regression analysis with osteoporosis status as a dependent variable clearly showed that age, BMR and IL-34 levels were independently and significantly associated with osteoporosis. The calculated odds ratios (OR) were 1.66 (95% CI = 1.16-2.38) for IL-34 levels and 0.22 (95% CI = 0.07-0.65) for BMR.

CONCLUSION

The significant (fourfold) elevation of IL-34 plasma levels in osteoporosis patients suggests that circulating IL-34 could be used as a biomarker for osteoporosis.

Exome sequencing links the SUMO protease SENP7 with fatal arthrogryposis multiplex congenita, early respiratory failure and neutropenia

BACKGROUND

SUMOylation involves the attachment of small ubiquitin-like modifier (SUMO) proteins to specific lysine residues on thousands of substrates with target-specific effects on protein function. Sentrin-specific proteases (SENPs) are proteins involved in the maturation and deconjugation of SUMO. Specifically, SENP7 is responsible for processing polySUMO chains on targeted substrates including the heterochromatin protein 1α (HP1α).

METHODS

We performed exome sequencing and segregation studies in a family with several infants presenting with an unidentified syndrome. RNA and protein expression studies were performed in fibroblasts available from one subject.

RESULTS

We identified a kindred with four affected subjects presenting with a spectrum of findings including congenital arthrogryposis, no achievement of developmental milestones, early respiratory failure, neutropenia and recurrent infections. All died within four months after birth. Exome sequencing identified a homozygous stop gain variant in SENP7 c.1474C>T; p.(Gln492*) as the probable aetiology. The proband's fibroblasts demonstrated decreased mRNA expression. Protein expression studies showed significant protein dysregulation in total cell lysates and in the chromatin fraction. We found that HP1α levels as well as different histones and H3K9me3 were reduced in patient fibroblasts. These results support previous studies showing interaction between SENP7 and HP1α, and suggest loss of SENP7 leads to reduced heterochromatin condensation and subsequent aberrant gene expression.

CONCLUSION

Our results suggest a critical role for SENP7 in nervous system development, haematopoiesis and immune function in humans.

Pro-Inflammatory Biomarkers Combined with Body Composition Display a Strong Association with Knee Osteoarthritis in a Community-Based Study

Knee osteoarthritis (KOA) is one of the most common progressive, age-dependent chronic degenerative joint diseases. KOA often develops as a result of a gradual articular cartilage loss caused by its wear and tear. Numerous studies suggest that the degradation of the knee joint involves inflammatory components. This process is also associated with body composition, particularly being overweight and muscle mass loss. The present study aimed to search for novel circulating KOA inflammatory biomarkers, taking into account body composition characteristics. To this aim, we recruited 98 patients diagnosed and radiologically confirmed with KOA and 519 healthy controls from the Arab community in Israel. A panel of soluble molecules, related to inflammatory, metabolic, and musculoskeletal disorders, was measured by ELISA in plasma samples, while several body composition parameters were assessed with bioimpedance analysis. Statistical analysis, including multivariable logistic regression, revealed a number of the factors significantly associated with KOA, independently of age and sex. The most significant independent associations [OR (95% CI)] were fat body mass/body weight index-1.56 (1.20-2.02), systemic immune-inflammation index-4.03 (2.23-7.27), circulating vaspin levels-1.39 (1.15-1.68), follistatin/FSTL1 ratio-1.32 (1.02-1.70), and activin A/FSTL1 ratio-1.33 (1.01-1.75). Further clinical studies are warranted to confirm the relevance of these KOA-associated biological factors. Hereafter, they could serve as reliable biomarkers for KOA in the general human population.

Danon Disease: Entire LAMP2 Gene Deletion with Unusual Clinical Presentation-Case Report and Review of the Literature

Danon disease is a rare x-linked dominant multisystemic disorder with a clinical triad of severe cardiomyopathy, skeletal myopathy, and intellectual disability. It is caused by defects in the lysosome-associated membrane protein-2 (LAMP2) gene. Numerous different mutations in the LAMP2 protein have been described. Danon disease is typically lethal by the mid-twenties in male patients due to cardiomyopathy and heart failure. Female patients usually present with milder and variable symptoms. This report describes a 42-year-old father and his 3-year-old daughter presenting with mild manifestations of the disease. The father has normal intellectual development and normal physical activity. At the age of 13, he was diagnosed with mild ventricular pre-excitation known as Wolf-Parkinson-White syndrome (WPWs), very mild and mostly asymptomatic cardiomyopathy and left ventricular hypertrophy, and at about the age of 25 presented with visual impairment due to cone-rod dystrophy. His daughter showed normal development and very mild asymptomatic electrocardiographic WPWs abnormalities with left mild ventricular hypertrophy. Genetic testing revealed an Xq24 microdeletion encompassing the entire LAMP2 gene. Relevant literature was reviewed as a reference for the etiology, diagnosis, treatment and case management.

The Genetics of Glucose-6-Phosphate-Dehydrogenase (G6PD) and Uridine Diphosphate Glucuronosyl Transferase 1A1 (UGT1A1) Promoter Gene Polymorphism in Relation to Quantitative Biochemical G6PD Activity Measurement and Neonatal Hyperbilirubinemia

Glucose-6-phosphate dehydrogenase (G6PD) deficiency and polymorphism in uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) were associated with significant neonatal hyperbilirubinemia (NHB) and increased risk for kernicterus. However, quantitative screening tests for G6PD enzyme activity proved unsatisfactory in estimating the risk for significant NHB, especially in heterozygous females that could present phenotype overlap between normal homozygotes, heterozygotes, and deficient homozygotes, resulting in a continuum of intermediate G6PD activity.

OBJECTIVE

To examine the association of genotype and phenotype in newborns with decreased G6PD activity and its relation to NHB.

STUDY DESIGN

Quantitative G6PD enzyme activities were measured on umbilical cord blood samples. After accepting parental consent, samples were analyzed for G6PD mutations and UGT1A1 gene polymorphisms (number of TA repeats in the UGT1A1 promoter). The associations to quantitative G6PD activity and bilirubin levels were assessed.

RESULTS

28 females and 27 males were studied. The Mediterranean mutation (NM_001360016.2(G6PD): c.563C>T (p.Ser188Phe)) was responsible for most cases of G6PD deficiency (20 hemizygous males, 3 homozygous and 16 heterozygous females). The association between this mutation, decreased G6PD activity and higher bilirubin levels was confirmed. Heterozygosity to 6/7 TA repeats in the UGT1A1 promoter was associated with increased NHB, especially in female newborns with G6PD deficiency. However, it seems that the interaction between G6PD deficiency, UGT1A1 promoter polymorphism, and NHB is more complex, possibly involving other genetic interactions, not yet described. Despite genotyping females with G6PD deficiency, the overlap between the upper range of borderline and the lower range of normal G6PD activity could not be resolved.

CONCLUSIONS

The results of this study highlight the possibility for future implementation of molecular genetic screening to identify infants at risk for significant NHB, especially UGT1A1 polymorphism in heterozygous females with borderline G6PD deficiency. However, further studies are needed before such screening could be applicable to daily practice.

[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA]

BACKGROUND

Short stature is a common finding among the general population, mostly presented as an isolated phenotype. The syndromic short statute is rare and complex. Recently, we examined several patients from related families sharing both short stature and congenital dental abnormalities.

OBJECTIVES

1. Clinical characterization of syndromic short stature; 2. To find the disease mutation and evaluate the carrier state in the particular community.

METHODS

Clinical characterization- by medical history, medical records and physical examination; Homozygosity mapping - by using the Single nucleotide polymorphism (SNP) chromosomal microarrays (CMA) analysis and gene mutation detection by ABI Sanger sequence.

RESULTS

All patients present with short stature severe dental anomalies including enamel formation and mineralization defect, oligodontia, abnormal shape and retarded eruption. CMA analysis in 3 patients and 2 healthy members of four families was normal. One homozygote region in chromosome 11 (11p11.2- 11q13.3) was found in all patients. By using the candidate gene approach, amongst the 301 genes found within this region, only one, the LTBP3 gene (Latent Transforming Growth Factor-Beta-Binding Protein-3) has high priority for sequence. Hence, LTBP3 (OMIM-602090) pathogenic variant is responsible for "brachyolmia with amelogenesis imperfecta" also known as "Dental Anomalies and Short Stature (DASS)" (OMIM- 601216). We sequenced all 29 LTBP3 exons and a novel splice pathogenic variant, c.1346-1G>A chr11:65319629, in exon 8 was identified. The variant segregated well within healthy tested family members. We found a high carrier rate in the village (1:15).

CONCLUSIONS

We identified a novel and common LTBP3 gene pathogenic variant responsible for short stature, brachyolmia and amelogenesis imperfecta in Druze Arab patients.

The search for systemic biomarkers for monitoring degenerative lumbar spinal disorders

Objectives

In our previous study, we reported that low back pain (LBP) severity and disability significantly correlate with body composition and several blood biochemical factors. Herein, we tested the hypothesis that these covariates are associated with anatomical deformations of the lumbar spine, in particular, radiographic facet joint osteoarthritis (FJOA) and lumbar disc degeneration (LDD) features important contributors to LBP.

Methods

CT and MRI images of the lumbar spine were obtained from 200 individuals suffering from LBP-sciatica. We examined the FJOA and total LDD score - the sum of the scores of the three radiographic features (intervertebral disc herniation, osteophythosis and spondylolisthesis) at the L1 - S1 vertebral levels. By implementing a bioelectrical impedance analysis, we assessed the participants for body composition, specifically, extracellular water (ECW). Plasma levels of growth and differentiation factor 15 (GDF-15) and visceral adipose tissue-derived serine protease inhibitor (vaspin), were detected by ELISA.

Results

By conducting a series of multivariable regression analyses, we report that the circulating levels of GDF-15, vaspin, and ECW are significantly and independently associated with FJOA scores [β_GDF15 ​= ​0.38 ​± ​0.08, p ​= ​0.0001; β_VASPIN ​= ​0.36 ​± ​0.07, p ​= ​0.000004; β_ECW ​= ​0.24 ​± ​0.07, p ​= ​0.002]. The levels of GDF-15 (β ​= ​0.30 ​± ​0.10, p ​= ​0.007) and ECW (β ​= ​0.20 ​± ​0.09, p ​= ​0.03) were also found significantly associated with the LDD scores.

Conclusion

The obtained new data suggest that GDF-15, vaspin and ECW may serve as biomarkers for FJOA and LDD phenotypes.

Scoliosis and skeletal muscle mass are strongly associated with low back pain-related disability in humans: An evolutionary anthropology point of view

OBJECTIVES

To clarify the potential risk factors and etiology of low back pain (LBP)-related disability, including structural changes of the spine (spinal scoliosis) and body composition components in a population with a high prevalence of LBP.

METHODS

In this cross-sectional study, two self-reported validated questionnaires were used to collect back pain and disability data in an ethnically homogeneous family-based population sample (N = 1078). The scoliosis angle of trunk rotation was measured by a scoliometer on three spinal levels while the patient was bent forward. Body composition parameters, including relative to weight (WT), fat, relative skeletal muscle mass (SMM/WT), and total body water were determined by bioelectrical impedance analysis. Statistical analysis was conducted, accounting for the familial composition of the sample.

RESULTS

The mixed multiple regression analyses with several LBP-related phenotypes as dependent variables consistently showed significant independent associations with scoliosis and SMM/WT, irrespective of other covariates. The odds ratios (OR)/95% CI for scoliosis ranged between 1.40 (1.19-1.64) and 1.51 (1.27-1.80), and from 0.61(0.51-0.72), to 0.71(0.58-0.87) for SMM/WT, depending on the LBP phenotype. The genetic components of the respective correlations between the LBP-phenotypes and scoliosis or SMM/WT were negligible.

CONCLUSIONS

The associations between LBP-related conditions and postured scoliosis and SMM/WT were consistent and significant and therefore may serve as markers in predicting the development of LBP-related disability. We interpret the origin of these correlations as the evolutionary event due to the imperfect spine anatomy adaptation to a vertical posture resulting from a quick transition to bipedalism from a quadrupedal ancestor.

Chromosomal Microarray Analysis in Pregnancies With Corpus Callosum or Posterior Fossa Anomalies

OBJECTIVE

We investigated the detection rate of clinically significant chromosomal microarray analysis (CMA) results in pregnancies with sonographic diagnosis of fetal corpus callosum anomalies (CCA) or posterior fossa anomalies (PFA).

METHODS

All CMA tests in pregnancies with CCA or PFA performed between January 2015 and June 2020 were retrospectively evaluated from the Israeli Ministry of Health database. The rate of CMA with clinically significant (pathogenic or likely pathogenic) findings was calculated and compared to a local Israeli cohort of 5,541 pregnancies with normal ultrasound.

RESULTS

One hundred eighty-two pregnancies were enrolled: 102 cases with CCA and 89 with PFA (9 cases had both). Clinically significant CMA results were found in 7/102 of CCA (6.9%) and in 7/89 of PFA (7.9%) cases. The CMA detection rate in pregnancies with isolated CCA (2/57, 3.5%) or PFA (2/50, 4.0%) was lower than in nonisolated cases, including additional CNS and/or extra-CNS sonographic anomalies (CCA-5/45, 11.1%; PFA-5/39, 12.8%), but this was not statistically significant. However, the rate among pregnancies that had extra-CNS anomalies, with or without additional CNS involvement (CCA-5/24, 20.8%; PFA-5/29, 17.2%), was significantly higher compared to all other cases (p = 0.0075 for CCA; p = 0.035 for PFA). Risk of CMA with clinically significant results for all and nonisolated CCA or PFA pregnancies was higher compared to the background risk reported in the control cohort (p < 0.001), but was not significant for isolated cases.

CONCLUSIONS

Our findings suggest that CMA testing is beneficial for the genetic workup of pregnancies with CCA or PFA, and is probably most informative when additional extra-CNS anomalies are observed.

Deletions and amplifications of the IGH variable and constant regions:a novel prognostic parameter in patients with multiple myeloma

Cytogenetic abnormalities are a recognized factor in the pathogenesis of multiple myeloma (MM). While chromosomal translocations involving the IGH gene have been investigated and reported, the implications of deletions or amplifications in the IGH gene have been less frequently examined. We conducted a retrospective analysis of 260 patients with MM from Northern Israel. Fluorescent in situ hybridization (FISH) analysis of separated CD-138 positive cells was done on bone marrow samples collected between 2016 and 2018. We used IGH break apart probes to identify IGH abnormalities and performed statistical analysis of clinical and prognostic features, comparing the different cytogenetic groups. Deletions in the variable region of the IGH (IGHv) were found in 17.3 % (n = 45) of patients and correlated with significantly worse progression free survival (PFS) after two years of follow up (p = 0.008), as well as with a worse response to 1st line treatment (p = 0.037). The median PFS was 7.1 and 17.7 months in patients with and without IGHv deletion, respectively. PFS differences remained significant (p = 0.017) in subgroup analysis of patients with high-risk cytogenetics (n = 108, 19 with IGHv deletion). Overall survival was not significantly different in the two groups. Constant region (IGHc) amplifications, were less frequently found (6.15 %, n = 16), yet significantly correlated with worse PFS after two years of follow up (p = 0.023). This difference remained valid in the high-risk subgroup (p = 0.001). In Conclusion, we identified that deletion of the IGH variable region and amplification in the IGH constant region, are both associated with poor prognosis and inferior outcome in MM.

Chromosomal microarray findings in pregnancies with an isolated pelvic kidney

Objective To examine the risk for abnormal chromosomal microarray analysis (CMA) results among fetuses with an apparently isolated pelvic kidney. Methods Data from all CMA analyses performed due to an isolated pelvic kidney reported to the Israeli Ministry of Health between January 2013 and September 2016 were retrospectively obtained. Risk estimation was performed comparing the rate of abnormal observed CMA findings to the general population risk, based on a systematic review encompassing 9272 cases and on local data of 5541 cases. Results Of 120 pregnancies with an isolated pelvic kidney, two gain-of-copy number variants suggesting microduplication syndromes were demonstrated (1.67%). In addition, three variants of unknown significance were detected (2.5%). Conclusion The risk for clinically significant CMA findings among pregnancies with an isolated single pelvic kidney was not significantly different compared to both control populations. The results of our study question the practice of routine CMA analysis in fetuses with an isolated pelvic kidney.

Biallelic mutations in EXOC3L2 cause a novel syndrome that affects the brain, kidney and blood

BACKGROUND

Dandy-Walker malformation features agenesis/hypoplasia of the cerebellar vermis, cystic dilatation of the fourth ventricle and enlargement of posterior fossa. Although Dandy-Walker malformation is relatively common and several genes were linked to the syndrome, the genetic cause in the majority of cases is unknown.

OBJECTIVE

To identify the mutated gene responsible for Dandy-Walker malformation, kidney disease and bone marrow failure in four patients from two unrelated families.

METHODS

Medical assessment, sonographic, MRI and pathological studies were used to define phenotype. Chromosomal microarray analysis and whole-exome sequence were performed to unravel the genotype.

RESULTS

We report four subjects from two unrelated families with homozygous mutations in the Exocyst Complex Component 3-Like-2 gene (EXOC3L2).EXOC3L2 functions in trafficking of post-Golgi vesicles to the plasma membrane. In the first family a missense mutation in a highly conserved amino acid, p.Leu41Gln, was found in three fetuses; all had severe forms of Dandy-Walker malformation that was detectable by prenatal ultrasonography and confirmed by autopsy. In the second family, the affected child carried a nonsense mutation, p.Arg72*, and no detected protein. He had peritrigonal and cerebellar white matter abnormalities with enlargement of the ventricular trigones, developmental delay, pituitary hypoplasia, severe renal dysplasia and bone marrow failure.

CONCLUSION

We propose that biallelic EXOC3L2 mutations lead to a novel syndrome that affects hindbrain development, kidney and possibly the bone marrow.

Fatal thoracic aortic aneurysm and dissection in a large family with a novel MYLK gene mutation: delineation of the clinical phenotype

Background

Thoracic and abdominal aortic aneurysms and dissection often develop in hypertensive elderly patients. At higher risk are smokers and those who have a family history of aortic aneurysms. In most affected families, the aortic aneurysms and dissection is inherited in an autosomal dominant manner with decreased penetrance and variable expressivity. Mutations at two chromosomal loci, TAA1 at 11q23 and the TAA2 at 5q13–14, and eight genes, MYLK, MYH11, TGFBR2, TGFBR1, ACTA2, SMAD3, TGFB2, and MAT2A, have been identified as being responsible for the disease in 23% of affected families.

Results

Herein, we inform on the clinical, genetic and pathological characteristics of nine living and deceased members of a large consanguineous Arab family with thoracic aortic aneurysm and dissection who carry a missense mutation c.4471G > T (Ala1491Ser), in exon 27 of MYLK gene. We show a reduced kinase activity of the Ala1491Ser protein compared to wildtype protein. This mutation is expressed as aortic aneurysm and dissection in one of two distinct phenotypes. A severe fatal and early onset symptom in homozygous or mild late onset in heterozygous genotypes.

Conclusions

We found that MYLK gene Ala1491Ser mutation affect the kinase activity and clinically, it presents with vascular aneurysms and dissection. We describe a distinct genotype phenotype correlation where; heterozygous patients have mild late onset and incomplete penetrance disease compared with the early onset severe and generally fatal outcome in homozygous patients.

Sequence variation in PPP1R13L results in a novel form of cardio-cutaneous syndrome

Dilated cardiomyopathy (DCM) is a life-threatening disorder whose genetic basis is heterogeneous and mostly unknown. Five Arab Christian infants, aged 4-30 months from four families, were diagnosed with DCM associated with mild skin, teeth, and hair abnormalities. All passed away before age 3. A homozygous sequence variation creating a premature stop codon at PPP1R13L encoding the iASPP protein was identified in three infants and in the mother of the other two. Patients' fibroblasts and PPP1R13L-knocked down human fibroblasts presented higher expression levels of pro-inflammatory cytokine genes in response to lipopolysaccharide, as well as Ppp1r13l-knocked down murine cardiomyocytes and hearts of Ppp1r13l-deficient mice. The hypersensitivity to lipopolysaccharide was NF-κB-dependent, and its inducible binding activity to promoters of pro-inflammatory cytokine genes was elevated in patients' fibroblasts. RNA sequencing of Ppp1r13l-knocked down murine cardiomyocytes and of hearts derived from different stages of DCM development in Ppp1r13l-deficient mice revealed the crucial role of iASPP in dampening cardiac inflammatory response. Our results determined PPP1R13L as the gene underlying a novel autosomal-recessive cardio-cutaneous syndrome in humans and strongly suggest that the fatal DCM during infancy is a consequence of failure to regulate transcriptional pathways necessary for tuning cardiac threshold response to common inflammatory stressors.

Homozygous LIPE mutation in siblings with multiple symmetric lipomatosis, partial lipodystrophy, and myopathy

Despite considerable progress in identifying causal genes for lipodystrophy syndromes, the molecular basis of some peculiar adipose tissue disorders remains obscure. In an Israeli-Arab pedigree with a novel autosomal recessive, multiple symmetric lipomatosis (MSL), partial lipodystrophy and myopathy, we conducted exome sequencing of two affected siblings to identify the disease-causing mutation. The 41-year-old female proband and her 36-year-old brother reported marked accumulation of subcutaneous fat in the face, neck, axillae, and trunk but loss of subcutaneous fat from the lower extremities and progressive distal symmetric myopathy during adulthood. They had increased serum creatine kinase levels, hypertriglyceridemia and low levels of high-density lipoprotein cholesterol. Exome sequencing identified a novel homozygous NC_000019.9:g.42906092C>A variant on chromosome 19, leading to a NM_005357.3:c.3103G>T nucleotide change in coding DNA and corresponding p.(Glu1035*) protein change in hormone sensitive lipase (LIPE) gene as the disease-causing variant. Sanger sequencing further confirmed the segregation of the mutation in the family. Hormone sensitive lipase is the predominant regulator of lipolysis from adipocytes, releasing free fatty acids from stored triglycerides. The homozygous null LIPE mutation could result in marked inhibition of lipolysis from some adipose tissue depots and thus may induce an extremely rare phenotype of MSL and partial lipodystrophy in adulthood associated with complications of insulin resistance, such as diabetes, hypertriglyceridemia and hepatic steatosis. © 2016 Wiley Periodicals, Inc.

Morbid obesity resulting from inactivation of the ciliary protein CEP19 in humans and mice

Obesity is a major public health concern, and complementary research strategies have been directed toward the identification of the underlying causative gene mutations that affect the normal pathways and networks that regulate energy balance. Here, we describe an autosomal-recessive morbid-obesity syndrome and identify the disease-causing gene defect. The average body mass index of affected family members was 48.7 (range = 36.7-61.0), and all had features of the metabolic syndrome. Homozygosity mapping localized the disease locus to a region in 3q29; we designated this region the morbid obesity 1 (MO1) locus. Sequence analysis identified a homozygous nonsense mutation in CEP19, the gene encoding the ciliary protein CEP19, in all affected family members. CEP19 is highly conserved in vertebrates and invertebrates, is expressed in multiple tissues, and localizes to the centrosome and primary cilia. Homozygous Cep19-knockout mice were morbidly obese, hyperphagic, glucose intolerant, and insulin resistant. Thus, loss of the ciliary protein CEP19 in humans and mice causes morbid obesity and defines a target for investigating the molecular pathogenesis of this disease and potential treatments for obesity and malnutrition.

Early metabolic defects in Arab subjects with strong family history of Type 2 diabetes

AIMS AND OBJECTIVE

It is widely accepted that the genetic make-up of the subject plays a pivotal role in the development of insulin resistance and β cell failure. The objective of this study was to examine whether the same or distinct genetic backgrounds contribute to the development of insulin resistance and β cell failure.

METHODS

We examined insulin sensitivity and β cell function in lean normal glucose tolerance subjects from 3 multigeneration Arab families. Families 1 and 2 had strong history of Type 2 diabetes (T2DM), while no member of family 3 had T2DM.

RESULTS

Subjects in family 1 manifested increased basal plasma free fatty acid (FFA) concentration and impaired suppression of plasma FFA during the OGTT compared to subjects in family 3. Subjects in family 2 had comparable fasting plasma FFA and suppression of plasma FFA during the OGTT to family 3. Both the absolute plasma glucose concentrations, and incremental area under the plasma glucose curve (ΔG0-120) during the OGTT were comparable in subjects of families 1 and 2, and were decreased in subjects of family 3. Whole body and muscle insulin sensitivity were comparable in subjects from families 2 and 3, and both were significantly decreased in subjects of family 1. Beta cell function was comparable in subjects of families 1 and 3 and was significantly decreased in subjects of family 2.

CONCLUSION

These results demonstrate that distinct genetic background contributes to the development of insulin resistance and β cell dysfunction in Arab individuals.

TBC1D24 mutation associated with focal epilepsy, cognitive impairment and a distinctive cerebro-cerebellar malformation

We describe the clinical and radiological features of a family with a homozygous mutation in TBC1D24. The phenotype comprised onset of focal seizures at 2 months with prominent eye-blinking, facial and limb jerking with an oral sensory aura. These were controllable with medication but persisted into adult life. Associated features were mild to moderate intellectual disability and cerebellar features. MRI showed subtle cortical thickening with cerebellar atrophy and high signal confined to the ansiform lobule. The disorder is allelic with familial infantile myoclonic epilepsy, where intellect and neurologic examination are normal, highlighting the phenotypic variation with mutations of TBC1D24.

A system for exact and approximate genetic linkage analysis of SNP data in large pedigrees

MOTIVATION

The use of dense single nucleotide polymorphism (SNP) data in genetic linkage analysis of large pedigrees is impeded by significant technical, methodological and computational challenges. Here we describe Superlink-Online SNP, a new powerful online system that streamlines the linkage analysis of SNP data. It features a fully integrated flexible processing workflow comprising both well-known and novel data analysis tools, including SNP clustering, erroneous data filtering, exact and approximate LOD calculations and maximum-likelihood haplotyping. The system draws its power from thousands of CPUs, performing data analysis tasks orders of magnitude faster than a single computer. By providing an intuitive interface to sophisticated state-of-the-art analysis tools coupled with high computing capacity, Superlink-Online SNP helps geneticists unleash the potential of SNP data for detecting disease genes.

RESULTS

Computations performed by Superlink-Online SNP are automatically parallelized using novel paradigms, and executed on unlimited number of private or public CPUs. One novel service is large-scale approximate Markov Chain-Monte Carlo (MCMC) analysis. The accuracy of the results is reliably estimated by running the same computation on multiple CPUs and evaluating the Gelman-Rubin Score to set aside unreliable results. Another service within the workflow is a novel parallelized exact algorithm for inferring maximum-likelihood haplotyping. The reported system enables genetic analyses that were previously infeasible. We demonstrate the system capabilities through a study of a large complex pedigree affected with metabolic syndrome.

AVAILABILITY

Superlink-Online SNP is freely available for researchers at http://cbl-hap.cs.technion.ac.il/superlink-snp. The system source code can also be downloaded from the system website.

CONTACT

omerw@cs.technion.ac.il

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

The association between vitamin D levels and recurrent group A streptococcal tonsillopharyngitis in adults

OBJECTIVES

To determine the association between recurrent group A streptococcal (GAS) tonsillopharyngitis and serum 25-hydroxy (25(OH)) vitamin D among adult subjects.

METHODS

Adult patients with tonsillopharyngitis between January 2007 and December 2009 were reviewed and identified retrospectively. Cases with a medical history of recurrent GAS tonsillopharyngitis were compared to age- and gender-matched individuals without a medical history of GAS tonsillopharyngitis. Recurrent tonsillopharyngitis was defined as three or more episodes of GAS tonsillopharyngitis per year for a period of two consecutive years.

RESULTS

Fifty-four cases with recurrent GAS tonsillopharyngitis and 50 controls were enrolled. There were no significant differences between cases and controls with regard to mean age (41 ± 13 vs. 42 ± 12 years; p=0.7) and male gender (55% vs. 54%; p=0.6). Mean serum levels of 25(OH) vitamin D among subjects with recurrent GAS tonsillopharyngitis were significantly lower from the controls (11.5 ng/ml ± 4.7 vs. 26 ng/ml ± 7; p=0.001). Multiple regression analysis showed that a serum 25(OH) vitamin D level <20 ng/ml was associated with recurrent GAS tonsillopharyngitis (odds ratio 1.62, 95% confidence interval 1.51-1.76; p < 0.001).

CONCLUSIONS

Our findings indicate a link between vitamin D deficiency and the recurrence of GAS tonsillopharyngitis.

Mechanisms linking nonalcoholic fatty liver disease with coronary artery disease

The most common cause of death in patients with nonalcoholic fatty liver disease (NAFLD) is coronary artery disease (CAD), not chronic liver disease. Fatty liver increases cardiovascular risk by classical (dyslipidemia, hypertension, diabetes) and by less conventional mechanisms. Common pathways involved in the pathogenesis of fatty liver and CAD includes hepatic insulin resistance and sub clinical inflammation. The hepatic insulin resistance state of fatty liver infiltration is characterized by increased FFA, which causes lipotoxicity and impairs endothelium-dependent vasodilatation, increases oxidative stress, and has a cardio toxic effect. Additional metabolic risk factors include leptin, adiponectin, pro inflammatory cytokines [such as IL-6, C-reactive protein and plasminogen activator inhibitor-1 (PAI-1)], which together lead to increased oxidative stress and endothelial dysfunction, finally promoting coronary artery disease (CAD). When classical risk factors are superimposed on fatty liver accumulation, they may further increase the new metabolic risk factors, exacerbating CAD. The clinical implication is that patients with NAFLD are at higher risk (steatohepatitis, diabetes, obesity, atherogenic dyslipidemia) and should undergo periodic cardiovascular risk assessment including the Framingham score, cardiac effort test, and measurement of intimae-media thickening of the carotids arteries. This may improve risk stratification for CAD.

A focal epilepsy and intellectual disability syndrome is due to a mutation in TBC1D24

We characterized an autosomal-recessive syndrome of focal epilepsy, dysarthria, and mild to moderate intellectual disability in a consanguineous Arab-Israeli family associated with subtle cortical thickening. We used multipoint linkage analysis to map the causative mutation to a 3.2 Mb interval within 16p13.3 with a LOD score of 3.86. The linked interval contained 160 genes, many of which were considered to be plausible candidates to harbor the disease-causing mutation. To interrogate the interval in an efficient and unbiased manner, we used targeted sequence enrichment and massively parallel sequencing. By prioritizing unique variants that affected protein translation, a pathogenic mutation was identified in TBC1D24 (p.F251L), a gene of unknown function. It is a member of a large gene family encoding TBC domain proteins with predicted function as Rab GTPase activators. We show that TBC1D24 is expressed early in mouse brain and that TBC1D24 protein is a potent modulator of primary axonal arborization and specification in neuronal cells, consistent with the phenotypic abnormality described.

Intra-familial clinical heterogeneity: absence of genotype-phenotype correlation in primary hyperoxaluria type 1 in Israel

BACKGROUND/AIMS

Primary hyperoxaluria type 1 (PH1) is caused by the deficiency of the liver enzyme alanine:glyoxylate aminotransferase which results in increased synthesis and excretion of oxalate. The clinical manifestations of PH1 are heterogeneous with respect to the age of onset and rate of progression. The aim of this study was to investigate possible relationships between a given genotype, the biochemical profile and the clinical phenotype.

METHODS

We conducted a study of 56 patients from 22 families with PH1 from Israel. The clinical and biochemical data were compiled and the genotype was determined for each family.

RESULTS

The prevalent phenotype was of early onset with progression to end-stage renal disease during the first decade of life. Fifteen PH1-causing mutations were detected in 21 families: 10 were first described in this patient population. Marked intra-familial clinical heterogeneity was noted, meaning that there was no correlation between a given genotype and the phenotype.

CONCLUSIONS

The clinical course of patients with PH1 is not dictated primarily by its genotype. Other genetic and/or environmental factors play a role in determining the ultimate phenotype.

Crohn disease: frequency and nature of CARD15 mutations in Ashkenazi and Sephardi/Oriental Jewish families

Crohn disease (CD), an inflammatory bowel disease, is a multifactorial trait with the highest frequency in Ashkenazi Jewish (AJ) individuals of Central European origin. Recently, three common predisposing CARD15 mutations (R702W, G908R, and 1007fs) and a polymorphism (P268S) were identified. To determine whether CARD15 mutations account for the higher prevalence of CD in AJ individuals, the haplotypes and allele frequencies of the common mutations and variants were assessed in 219 members of 50 AJ and 53 members of 10 Sephardi/Oriental Jewish (SOJ) multiplex families with CD, in 36 AJ patients with sporadic CD, and in 246 AJ and 82 SOJ controls. A higher frequency of CARD15 mutations was found in AJ patients from multiplex families with CD from Central (44.0%) versus Eastern (24.0%) Europe, especially for G908R and 1007fs, and in SOJ patients (34.5%) compared with AJ (10.1%) or SOJ (5.4%) controls. Contrary to expectation, the frequency of the common mutations was slightly lower in AJ patients with CD (30.1%) than in SOJ patients with CD (34.5%). The 702W allele was associated with both the P268 and 268S alleles. CARD15 mutation frequencies were greater in affected sib pairs than in sporadic CD cases but actually decreased in families with three or more affected sibs, raising the possibility of genetic heterogeneity. Similarly, our linkage evidence on chromosome 16 was diminished in the families with three or more affected sibs compared with sib pairs. Screening the CARD15 gene for rare variants revealed five novel changes (D113N, D357A, I363F, L550V, and N852S) of which N852S occurred only in AJ individuals and may be disease predisposing. Also, there was no evidence for increased risk associated with the recently described IVS(+158) single-nucleotide polymorphism. Although the AJ controls appear to have a higher frequency of CARD15 mutations than the SOJ controls, it is unlikely that this difference fully explains the excess frequency of CD in the AJ population.

The deoxyguanosine kinase gene is mutated in individuals with depleted hepatocerebral mitochondrial DNA

Mitochondrial DNA (mtDNA)-depletion syndromes (MDS; OMIM 251880) are phenotypically heterogeneous, autosomal-recessive disorders characterized by tissue-specific reduction in mtDNA copy number. Affected individuals with the hepatocerebral form of MDS have early progressive liver failure and neurological abnormalities, hypoglycemia and increased lactate in body fluids. Affected tissues show both decreased activity of the mtDNA-encoded respiratory chain complexes (I, III, IV, V) and mtDNA depletion. We used homozygosity mapping in three kindreds of Druze origin to map the gene causing hepatocerebral MDS to a region of 6.1 cM on chromosome 2p13, between markers D2S291 and D2S2116. This interval encompasses the gene (DGUOK) encoding the mitochondrial deoxyguanosine kinase (dGK). We identified a single-nucleotide deletion (204delA) within the coding region of DGUOK that segregates with the disease in the three kindreds studied. Western-blot analysis did not detect dGK protein in the liver of affected individuals. The main supply of deoxyribonucleotides (dNTPs) for mtDNA synthesis comes from the salvage pathway initiated by dGK and thymidine kinase-2 (TK2). The association of mtDNA depletion with mutated DGUOK suggests that the salvage-pathway enzymes are involved in the maintenance of balanced mitochondrial dNTP pools.

Exogenous ascorbic acid (vitamin C) increases resistance to salt stress and reduces lipid peroxidation

The transition from reversible to permanent wilting, in whole tomato seedlings (Lycopersicon esculentum Mill. cv. M82) following severe salt-stress by root exposure to 300 mM NaCl, was investigated. Salinized seedlings wilted rapidly but recovered if returned to non-saline nutrient solution within 6 h. However, after 9 h of salt-treatment 100% of the seedlings remained wilted and died. Remarkably, the addition of an anti-oxidant (0.5 mM ascorbic acid) to the root medium, prior to and during salt-treatment for 9 h, facilitated the subsequent recovery and long-term survival of c. 50% of the wilted seedlings. Other organic solutes without known anti-oxidant activity were not effective. Salt-stress increased the accumulation in roots, stems and leaves, of lipid peroxidation products produced by interactions with damaging active oxygen species. Additional ascorbic acid partially inhibited this response but did not significantly reduce sodium uptake or plasma membrane leakiness.

Hypotrichosis with juvenile macular dystrophy is caused by a mutation in CDH3, encoding P-cadherin

Congenital hypotrichosis associated with juvenile macular dystrophy (HJMD; MIM601553) is an autosomal recessive disorder of unknown etiology, characterized by hair loss heralding progressive macular degeneration and early blindness. We used homozygosity mapping in four consanguineous families to localize the gene defective in HJMD to 16q22.1. This region contains CDH3, encoding P-cadherin, which is expressed in the retinal pigment epithelium and hair follicles. Mutation analysis shows in all families a common homozygous deletion in exon 8 of CDH3. These results establish the molecular etiology of HJMD and implicate for the first time a cadherin molecule in the pathogenesis of a human hair and retinal disorder.

Androgenetic alopecia in heterozygous carriers of a mutation in the human hairless gene

BACKGROUND

Androgenetic alopecia is considered to be genetically determined. Recently, a rare autosomal recessive form of hereditary alopecia, termed atrichia with papular lesions (APL), was found to result from mutations in the human hairless gene.

OBJECTIVE

Our aim was to assess the pattern of androgenetic alopecia in heterozygous carriers of a deleterious mutation in the human hairless gene.

METHODS

Healthy male second-degree relatives (n = 31) of patients affected with APL and belonging to a large consanguineous kindred were interviewed and given a Hamilton score of baldness. DNA was obtained from each subject and analyzed for the presence of a mutation in the human hairless gene known to affect this family. The age at onset and extent of baldness were compared in healthy homozygotes and heterozygous carriers of the mutation.

RESULTS

Statistical analysis of the results revealed no differences in age at onset and extent of androgenetic alopecia between the two groups of subjects.

CONCLUSION

The present study reports the first attempt to characterize the phenotype of heterozygous carriers of a mutation in the human hairless gene. It indicates that the presence of a deleterious mutation in one allele of the hairless gene does not affect the pattern of androgenetic hair loss.

Absorption of iron in rats with experimental enteritis

Inflammatory conditions of the gastrointestinal tract and iron-deficiency anemia are very common in humans. Acute intestinal inflammation was pathologically established in rats by intraluminal administration of acetic acid into the duodenum and the proximal jejunum. The study included two control groups of intact (untreated) rats and sham-operated (saline-treated) rats for each intestinal segment. A third group of rats received acetic acid. The acetic acid-induced inflammatory process was established histopathologically and biochemically. Two days after treatment, iron absorption was measured using ligated 10-cm loops of proximal jejunum or ligated duodenum in which 59Fe was injected intraluminally (n = 6 in each group). In another four control groups (intact and sham-operated for each intestinal segment) and two acetic acid-treated groups, serosal-luminal secretion of 59Fe was measured after intravenous injection (n = 5 in each group). 59Fe transfer from the lumens of the duodenum and jejunum to the portal system was significantly lower in those rats in whom inflammation was induced by acetic acid. There was no apparent serosal-luminal secretion of intravenously injected 59Fe in any of the studied groups. We conclude that acetic acid-induced intestinal inflammation significantly reduces iron absorption by the duodenum and the proximal jejunum.

Prenatal diagnosis and carrier detection for molybdenum cofactor deficiency type A in northern Israel using polymorphic DNA markers

Molybdenum cofactor deficiency (MoCoD) is an autosomal recessive, fatal neurological disorder, characterized by the combined deficiency of sulphite oxidase, xanthine dehydrogenase and aldehyde oxidase. We have recently reported an excessive occurrence of this fatal disorder among segments of the Arab population in Northern Israel suggesting that the true incidence of MoCoD is probably underestimated in this highly inbred population. This lethal disease can be diagnosed prenatally by assay of sulphite oxidase activity in chorionic villus samples in pregnancies of couples who have had previously affected children (obligatory carriers). However, to date, there is no biochemical assay for carrier detection among the population at risk. Recently we demonstrated the linkage of a MoCoD gene to an 8-cM region on chromosome 6p21.3 in two consanguineous Israeli-Arab unrelated kindreds. The description of the MOCS1 gene that maps to the same region and which carries multiple mutations in MoCoD type A followed this finding. We describe here one additional kindred of Arab-Israeli origin, which is also linked to the MOCS1 locus, and demonstrate the feasibility of prenatal diagnosis and carrier detection using microsatellite markers in selected families when mutations are unknown. A complete correlation between the biochemical and DNA assays was found in a total of six samples (five chorionic villus and one amniocyte culture sample) obtained from the three MoCoD families.

Mutations in SLC19A2 cause thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and deafness

Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270). We have previously narrowed the TRMA locus from a 16-cM to a 4-cM interval on chromosomal region 1q23.3 (refs 3,4) and this region has been further refined to a 1.4-cM interval. Previous studies have suggested that deficiency in a high-affinity thiamine transporter may cause this disorder. Here we identify the TRMA gene by positional cloning. We assembled a P1-derived artificial chromosome (PAC) contig spanning the TRMA candidate region. This clarified the order of genetic markers across the TRMA locus, provided 9 new polymorphic markers and narrowed the locus to an approximately 400-kb region. Mutations in a new gene, SLC19A2, encoding a putative transmembrane protein homologous to the reduced folate carrier proteins, were found in all affected individuals in six TRMA families, suggesting that a defective thiamine transporter protein (THTR-1) may underlie the TRMA syndrome.

Localization of a gene for molybdenum cofactor deficiency, on the short arm of chromosome 6, by homozygosity mapping

Molybdenum cofactor deficiency (MoCoD) is a fatal disorder manifesting, shortly after birth, with profound neurological abnormalities, mental retardation, and severe seizures unresponsive to any therapy. The disease is a monogenic, autosomal recessive disorder, and the existence of at least two complementation groups suggests genetic heterogeneity. In humans, MoCoD leads to the combined deficient activities of sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. By using homozygosity mapping and two consanguineous affected kindreds of Israeli-Arab origin, including five patients, we demonstrated linkage of a MoCoD gene to an 8-cM region on chromosome 6p21.3, between markers D6S1641 and D6S1672. Linkage analysis generated the highest combined LOD-score value, 3.6, at a recombination fraction of 0, with marker D6S1575. These results now can be used to perform prenatal diagnosis with microsatellite markers. They also provide the only tool for carrier detection of this fatal disorder.