Heterozygous Genetic Variants Research Articles

Rare heterozygous genetic variants of NRXN and NLGN gene families involved in synaptic function and their association with neurodevelopmental disorders.

The interaction of neurexins (NRXNs) in the presynaptic membrane with postsynaptic cell adhesion molecules called neuroligins (NLGNs) is critical for this synaptic function. Impaired synaptic functions are emphasized in neurodevelopmental disorders to uncover etiological factors. We evaluated variants in NRXN and NLGN genes encoding molecules located directly at the synapse in patients with neuropsychiatric disorders using clinical exome sequencing and chromosomal microarray. We presented detailed clinical findings of cases carrying heterozygous NRXN1 (c.190C>T, c.1679C>T and two copy number variations [CNVs]), NRXN2 (c.808dup, c.1901G>T), NRXN3 (c.3889C>T), and NLGN1 (c.269C>G, c.473T>A) gene variants. In addition, three novel variants were identified in the NRXN1 (c.1679C>T), NRXN3 [c.3889C>T (p.Pro1297Ser)], and NLGN1 [c.473T>A (p.Ile158Lys)] genes. We emphasize the clinical findings of CNVs of the NRXN1 gene causing a more severe clinical presentation than single nucleotide variants of the NRXN1 gene in this study. We detected an NRXN2 gene variant (c.808dup) with low allelic frequency in two unrelated cases with the same diagnosis. We emphasize the importance of this variant for future studies. We suggest that NRXN2, NRXN3, and NLGN1 genes, which are less frequently reported than NRXN1 gene variants, may also be associated with neurodevelopmental disorders.

A long-read sequencing strategy with overlapping linkers on adjacent fragments (OLAF-Seq) for targeted resequencing and enrichment

In this report, we present OLAF-Seq, a novel strategy to construct a long-read sequencing library such that adjacent fragments are linked with end-terminal duplications. We use the CRISPR-Cas9 nickase enzyme and a pool of multiple sgRNAs to perform non-random fragmentation of targeted long DNA molecules (> 300kb) into smaller library-sized fragments (about 20 kbp) in a manner so as to retain physical linkage information (up to 1000 bp) between adjacent fragments. DNA molecules targeted for fragmentation are preferentially ligated with adaptors for sequencing, so this method can enrich targeted regions while taking advantage of the long-read sequencing platforms. This enables the sequencing of target regions with significantly lower total coverage, and the genome sequence within linker regions provides information for assembly and phasing. We demonstrated the validity and efficacy of the method first using phage and then by sequencing a panel of 100 full-length cancer-related genes (including both exons and introns) in the human genome. When the designed linkers contained heterozygous genetic variants, long haplotypes could be established. This sequencing strategy can be readily applied in both PacBio and Oxford Nanopore platforms for both long and short genes with an easy protocol. This economically viable approach is useful for targeted enrichment of hundreds of target genomic regions and where long no-gap contigs need deep sequencing.

Complement dysregulation associated with a genetic variant in factor H-related protein 5 in atypical hemolytic uremic syndrome.

Atypical hemolytic uremic syndrome (aHUS) can be associated with mutations, deletions, or hybrid genes in factor H-related (FHR) proteins. A child with aHUS was investigated. Genetics was assessed by Sanger and next generation sequencing. Serum FHR5 was evaluated by immunoblotting, ELISA, and by induction of rabbit red blood cell hemolysis in the presence/absence of recombinant human rFHR5. Mutagenesis was performed in HEK cells. A heterozygous genetic variant in factor H-related protein 5 (CFHR5), M514R, was found in the child, who also had a homozygous deletion of CFHR3/CFHR1, and antibodies to factor H, as well as low levels of C3. Patient serum exhibited low levels of FHR5. In the presence of rabbit red blood cells, patient serum induced hemolysis which decreased when rFHR5 was added at physiological concentrations. Similar results were obtained using serum from the father, bearing the CFHR5 variant without factor H antibodies. Patient FHR5 formed normal dimers. The CFHR5 M514R variant was expressed in HEK cells and minimal secretion was detected whereas the protein level was elevated in cell lysates. Decreased secretion of the product of the mutant allele could explain the low FHR5 levels in patient serum. Reduced hemolysis when rFHR5 was added to serum suggests a regulatory role regarding complement activation on red blood cells. As such, low levels of FHR5, as demonstrated in the patient, may contribute to complement activation.

Rare Variants in LRP4 Are Associated with Mesiodens, Root Maldevelopment, and Oral Exostoses in Humans

Low density lipoprotein receptor-related protein 4 (LRP4; MIM 604270) modulates WNT/β-catenin signaling, through its binding of WNT ligands, and to co-receptors LRP5/6, and WNT inhibitors DKK1, SOSTDC1, and SOST. LRP4 binds to SOSTDC1 and WNT proteins establishing a negative feedback loop between Wnt/β-catenin, Bmp, and Shh signaling during the bud and cap stages of tooth development. Consistent with a critical role for this complex in developing teeth, mice lacking Lrp4 or Sostdc1 have multiple dental anomalies including supernumerary incisors and molars. However, there is limited evidence supporting variants in LRP4 in human dental pathologies. We clinically, radiographically, and molecularly investigated 94 Thai patients with mesiodens. Lrp4 mutant mice were generated in order to study the effects of aberrant Lrp4 expression in mice. Whole exome and Sanger sequencing identified three extremely rare variants (c.4154A>G, p.Asn1385Ser; c.3940G>A, p.Gly1314Ser; and c.448G>A, p.Asp150Asn) in LRP4 in seven patients with mesiodens. Two patients had oral exostoses and two patients had root maldevelopments. Supernumerary incisors were observed in Lrp4 mutant mice. Our study implicates heterozygous genetic variants in LRP4 as contributing factors in the presentation of mesiodens, root maldevelopments, and oral exostoses, possibly as a result of altered WNT/β-catenin-BMP-SHH signaling.

Genetic Variants of SIRT1 Gene Promoter in Type 2 Diabetes.

Type 2 diabetes (T2D) is a highly heterogeneous and polygenic disease. To date, genetic causes and underlying mechanisms for T2D remain unclear. SIRT1, one member of highly conserved NAD-dependent class III deacetylases, has been implicated in many human diseases. Accumulating evidence indicates that SIRT1 is involved in insulin resistance and impaired pancreatic β-cell function, the two hallmarks of T2D. Thus, we speculated that altered SIRT1 levels, resulting from the genetic variants within its regulatory region of SIRT1 gene, may contribute to the T2D development. In this study, the SIRT1 gene promoter was genetically analyzed in T2D patients (n = 218) and healthy controls (n = 358). A total of 20 genetic variants, including 7 single-nucleotide polymorphisms (SNPs), were identified. Five heterozygous genetic variants (g.4114-15InsA, g.4801G > A, g.4816G > C, g.4934G > T, and g.4963_64Ins17bp) and one SNP (g.4198A > C (rs35706870)) were identified in T2D patients, but in none of the controls. The frequencies of two SNPs (g.4540A > G (rs3740051) (OR: 1.75, 95% CI: 1.24-2.47, P < 0.001 in dominant genetic model) and g.4821G > T (rs35995735)) (OR: 3.58, 95% CI: 1.94-6.60, P < 0.001 in dominant genetic model) were significantly higher in T2D patients. Further association and haplotype analyses confirmed that these two SNPs were strongly linked, contributing to the T2D (OR: 1.442, 95% CI: 1.080-1.927, P < 0.05). Moreover, most of the genetic variants identified in T2D were disease-specific. Taken together, the genetic variants within SIRT1 gene promoter might contribute to the T2D development by altering SIRT1 levels. Underlying molecular mechanism needs to be further explored.

416 DESMOPLAKIN CARDIOMYOPATHY PRESENTING WITH CARDIAC ARREST IN A PATIENT WITH MYOCARDIAL NON-COMPACTION AND LEFT ACCESSORY PATHWAY

Abstract Introduction Desmoplakin is a human protein which plays a key role into desmosomes structure. Desmoplakin gene mutations can cause the so-called "desmoplakin cardiomyopathy", a form of arrhythmogenic cardiomyopathy. Its clinical history is characterized by severe ventricular arrhythmias, episodic myocardial injury and left ventricular systolic dysfunction associated with fibrosis. Case Presentation A 12-years-old male came to our inherited cardiomyopathy ambulatory for cardiological evaluation due to a previous history of cardiac arrest when he was infant (30 days newborn) and palpitation. Previous medical history included eczematous dermatitis and occasional hyperglycemia. During cardiological evaluation EKG was unremarkable, echocardiography revealed myocardial noncompaction in apical and mid-ventricular regions of the left ventricle's infero-lateral wall (end systolic ratio 2:1) and evidence of direct blood flow into deep intertrabecular recesses by colour doppler. Due to history of palpitation an EP study was performed that showed a lateral left-sided accessory pathway that was ablated during the same procedure. A genetic molecular analysis with exome sequencing (NGS, next generation sequencing) was performed and revealed a heterozygous genetic variant in DSP (Desmoplakin) gene on chromosome 6 (c.4046 G&amp;gt;A pSer1349Asn). Familiar screening revealed the same genetic variant in his father and his brother, both had no cardiological events. Conclusion Desmoplakin cardiomyopathy may have a severe clinical presentation with cardiac arrest. A multidisciplinary approach is suggested for a tailored management of these patients.

RF24 | PSUN96 Setmelanotide in Patients With Heterozygous POMC, LEPR, SRC1, or SH2B1 Obesity: Design of EMANATE – A Placebo-Controlled Phase 3 Trial

Abstract Background The central hypothalamic melanocortin-4 receptor (MC4R) pathway is a key regulator of energy balance. Certain variants in genes upstream of MC4R, including those encoding the leptin receptor (LEPR), proopiomelanocortin (POMC), steroid receptor coactivator 1 (SRC1; also known as NCOA1), prohormone convertase (PC)1/3 (encoded by the gene PCSK1), and SH2B adaptor protein 1 (SH2B1) genes, lead to impaired MC4R pathway signaling and rare genetic diseases of obesity. While the deficiencies resulting from these genetic variants differ in some clinical features, they are all characterized by hyperphagia (pathologic insatiable hunger) and early-onset obesity during childhood. Setmelanotide, an MC4R agonist, reduced body weight and hyperphagia (assessed by hunger scores) after 3 months in patients with heterozygous POMC, including patients with the N221D variant in PCSK1; LEPR; SRC1; and SH2B1 (including a 220–kilobase pair distal deletion of chromosome 16p11.2) variants in an earlier Phase 2 trial. In the Phase 2 trial, 12 of 35 (34%) patients with heterozygous POMC, PCSK1, or LEPR variants; 9 of 30 patients (30%) with heterozygous SRC1 variants; and 13 of 35 (37%) patients with heterozygous SH2B1 variants achieved ≥5% weight loss after 3 months of setmelanotide treatment. Methods EMANATE is a randomized, double-blind, placebo-controlled Phase 3 trial (NCT05093634) comprising 5 similar independent sub-studies based on genetic variants. For eligibility, patients must be 6-65 years old, have history of hyperphagia and childhood obesity, current obesity defined as BMI ≥30 kg/m2 (in those ≥18 years old), and BMI ≥95th percentile (in those 6-17 years old). Patients must also have a heterozygous genetic variant in POMC or PCSK1; heterozygous genetic variant in LEPR; a homozygous, heterozygous, or compound heterozygous variant in SRC1 or SH2B1 (including a chromosomal deletion of 16p11.2 including SH2B1); or a heterozygous N221D variant in PCSK1. Patients with ≥2% weight loss in the prior 3 months, HbA1C &amp;gt;10%, clinically significant pulmonary, cardiac, or oncological disease, or history of significant liver or serious kidney disease are not eligible. Within each sub-study, patients will be randomized 1: 1 to receive daily subcutaneous injections of setmelanotide or placebo for 52 weeks. The primary outcome is the mean change in body weight in patients who receive setmelanotide compared with placebo. Safety will be assessed by frequency and severity of adverse events. Current Status: EMANATE is currently underway and began enrolling patients in early 2022. The planned enrollment is 560 patients. If successful, this placebo-controlled Phase 3 trial will support setmelanotide treatment for improvements in body weight–related measures and hunger in an expanded population of patients living with rare genetic diseases of obesity. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 1:12 p.m. - 1:17 p.m.

Alström syndrome: Two clinical cases with two novel pathogenic variants.

To report two clinical cases of Alström syndrome (AS) with novel pathogenic variant of the ALMS1 gene not previously reported. Patient 1 was a 6-year-old female presenting with poor vision. Ophthalmic examination only showed a visual field (VF) with diffusely decreased sensitivity in both eyes. At age of 15, vision and ophthalmic examination remain stable. Patient 2 was a 2-year-old male with poor vision, photophobia, and nystagmus. ERG showed a severe decrease in cone and rod responses. At age of 6, his vision is lower than 0.1 (decimal scale) and VF is severely constricted. Both of them presented with dilated cardiomyopathy in their first's months of life and patient 2 developed sensorineural deafness along with follow-up. Research genetic testing revealed two loss-of-function heterozygous genetic variants in the ALMS1 gene in both patients, so the diagnosis of AS was made. AS is a rare disease caused by pathogenic variants of ALMS1 gene that causes ocular manifestations in almost 100% of patients. There are many genetic variants of AMLS1 described, but novel pathogenic variants can still be found. Ophthalmologists play an important role in the diagnosis, and AS should be included in the differential diagnosis when retinal dystrophy is suspected.

Heterozygous Genetic Variants in Autosomal Recessive Genes of the Leptin-Melanocortin Signalling Pathway Are Associated With the Development of Childhood Obesity.

Monogenic obesity is a severe, genetically determined disorder that affects up to 1/1000 newborns. Recent reports on potential new therapeutics and innovative clinical approaches have highlighted the need for early identification of individuals with rare genetic variants that can alter the functioning of the leptin-melanocortin signalling pathway, in order to speed up clinical intervention and reduce the risk of chronic complications. Therefore, next-generation DNA sequencing of central genes in the leptin-melanocortin pathway was performed in 1508 children and adolescents with and without obesity, aged 2-19 years. The recruited cohort comprised approximately 5% of the national paediatric population with obesity. The model-estimated effect size of rare variants in the leptin-melanocortin signalling pathway on longitudinal weight gain between carriers and non-carriers was derived. In total, 21 (1.4%) participants had known disease-causing heterozygous variants (DCVs) in the genes under investigation, and 62 (4.1%) participants were carriers of rare variants of unknown clinical significance (VUS). The estimated frequency of potential genetic variants associated with obesity (including rare VUS) ranged between 1/150 (VUS and DCV) and 1/850 (DCV) and differed significantly between participants with and without obesity. On average, the variants identified would result in approximately 7.6 kg (7.0-12.9 kg at the 95th percentile of body weight) (girls) and 8.4 kg (8.2-14.4 kg) (boys) of additional weight gain in carriers at age 18 years compared with subjects without obesity. In conclusion, children with a genetic predisposition to obesity can be promptly identified and may account for more than 6% of obesity cases. Early identification of genetic variants in the LEPR, PCSK1, POMC, MC3R and MC4R genes could reduce the societal burden and improve the clinical management of early severe childhood obesity and its implementation should be further investigated.

The Genetics of Inherited Cholestatic Disorders in Neonates and Infants: Evolving Challenges.

Many inherited conditions cause cholestasis in the neonate or infant. Next-generation sequencing methods can facilitate a prompt diagnosis in some of these cases; application of these methods in patients with liver diseases of unknown cause has also uncovered novel gene-disease associations and improved our understanding of physiological bile secretion and flow. By helping to define the molecular basis of certain cholestatic disorders, these methods have also identified new targets for therapy as well patient subgroups more likely to benefit from specific therapies. At the same time, sequencing methods have presented new diagnostic challenges, such as the interpretation of single heterozygous genetic variants. This article discusses those challenges in the context of neonatal and infantile cholestasis, focusing on difficulties in predicting variant pathogenicity, the possibility of other causal variants not identified by the genetic screen used, and phenotypic variability among patients with variants in the same genes. A prospective, observational study performed between 2010–2013, which sequenced six important genes (ATP8B1, ABCB11, ABCB4, NPC1, NPC2 and SLC25A13) in an international cohort of 222 patients with infantile liver disease, is given as an example of potential benefits and challenges that clinicians could face having received a complex genetic result. Further studies including large cohorts of patients with paediatric liver disease are needed to clarify the spectrum of phenotypes associated with, as well as appropriate clinical response to, single heterozygous variants in cholestasis-associated genes.

Acute Trem2 reduction triggers increased microglial phagocytosis, slowing amyloid deposition in mice

Heterozygous genetic variants within the TREM2 gene show a strong association with increased Alzheimer's disease (AD) risk. Amyloid beta-depositing mouse models haploinsufficient or null for Trem2 have identified important relationships among TREM2, microglia, and AD pathology; however, results are challenging to interpret in the context of varying microglial phenotypes and disease progression. We hypothesized that acute Trem2 reduction may alter amyloid pathology and microglial responses independent of genetic Trem2 deletion in mouse models. We developed antisense oligonucleotides (ASOs) that potently but transiently lower Trem2 messenger RNA throughout the brain and administered them to APP/PS1 mice at varying stages of plaque pathology. Late-stage ASO-mediated Trem2 knockdown significantly reduced plaque deposition and attenuated microglial association around plaque deposits when evaluated 1 mo after ASO injection. Changes in microglial gene signatures 1 wk after ASO administration and phagocytosis measured in ASO-treated cells together indicate that microglia may be activated with short-term Trem2 reduction. These results suggest a time- and/or dose-dependent role for TREM2 in mediating plaque deposition and microglial responses in which loss of TREM2 function may be beneficial for microglial activation and plaque removal in an acute context.

Genetic and Clinical Characteristics of A Family with Combined PROC and PROS1 Genetic Variants

To test the anticoagulation functions, perform the genetic diagnosis and analyze the clinical characteristics in a family with combined heterozygous genetic variants of PROC and PROS1. Peripheral blood was collected from all the family members. Hematological phenotypes and activity of anticoagulant factors were analyzed. Target genes were amplified by PCR from DNA isolated from peripheral blood, and then were analyzed by Sanger DNA sequencing. Many members in the family displayed the combined genetic variants in protein C and protein S, and six family members accompanied by deep venous thrombosis (DVT). The influences of genetic and secondary factors on the incidence of venous thrombosis in the family members were analyzed. The results showed that in this family, carriers of combined protein C and protein S gene defects had a higher incidence of VTE, but acquired factors still played a key role in the eventual thrombotic symptoms. Venous thromboembolism (VTE) is a multifactorial disease, the combined genetic heterozygous mutations of protein C and S is an important genetic factor, and the clinical phenotype show a high heterogenicity, the secondary factors contribute to the VTE incidence.

Genetic diagnosis of autoinflammatory disease patients using clinical exome sequencing.

Autoinflammatory diseases comprise a wide range of syndromes caused by dysregulation of the innate immune response. They are difficult to diagnose due to their phenotypic heterogeneity and variable expressivity. Thus, the genetic origin of the disease remains undetermined for an important proportion of patients. We aim to identify causal genetic variants in patients with suspected autoinflammatory disease and to test the advantages and limitations of the clinical exome gene panels for molecular diagnosis. Twenty-two unrelated patients with clinical features of autoinflammatory diseases were analyzed using clinical exome sequencing (~4800 genes), followed by bioinformatic analyses to detect likely pathogenic variants. By integrating genetic and clinical information, we found a likely causative heterozygous genetic variant in NFKBIA (p.D31N) in a North-African patient with a clinical picture resembling the deficiency of interleukin-1 receptor antagonist, and a heterozygous variant in DNASE2 (p.G322D) in a Spanish patient with a suspected lupus-like monogenic disorder. We also found variants likely to increase the susceptibility to autoinflammatory diseases in three additional Spanish patients: one with an initial diagnosis of juvenile idiopathic arthritis who carries two heterozygous UNC13D variants (p.R727Q and p.A59T), and two with early-onset inflammatory bowel disease harbouring NOD2 variants (p.L221R and p.A728V respectively). Our results show a similar proportion of molecular diagnosis to other studies using whole exome or targeted resequencing in primary immunodeficiencies. Thus, despite its main limitation of not including all candidate genes, clinical exome targeted sequencing can be an appropriate approach to detect likely causative variants in autoinflammatory diseases.

New variants in Spanish Niemann-Pick type c disease patients.

Niemann-Pick type C (NPC) disease is a rare inherited disease, with progressive neurodegeneration as the main symptom. It is a lysosomal storage disorder caused by mutations in NPC1 or NPC2 genes, leading to a lysosomal cholesterol trafficking impairment. Disease indicators are the clinical suspicion and biomarker levels. However, a genetic study is mandatory for the diagnosis, which is complicated due to the different variants with unknown significance. The aim of this work was to identify the variants responsible for NPC in our pediatric population. Twenty-two samples from non-related infants believed to have NPC disease were analyzed during the last 3years. Surrogate biomarkers of the disease were evaluated whenever possible. Sanger sequencing for both genes is reported for all samples. Complementary genetic studies were performed when necessary. NPC disease was confirmed in 31.8% of subjects due to homozygous or compound heterozygous genetic variants in NPC1. The following four novel variants were identified: a gross deletion variant composed of the gene promoter and the first exon, NM_000271.3:c.385delT, NM_000271.3:c.1553+1342_1655-291del, and NM_000271.3:c.1757delA. None had functional activity and all resulted in important structural changes in the protein.

Sudden arrhythmia death syndrome in young victims: a five-year retrospective review and two-year prospective molecular autopsy study by next-generation sequencing and clinical evaluation of their first-degree relatives.

Sudden arrhythmia death syndrome (SADS) accounts for about 30% of causes of sudden cardiac death (SCD) in young people. In Hong Kong, there are scarce data on SADS and a lack of experience in molecular autopsy. We aimed to investigate the value of molecular autopsy techniques for detecting SADS in an East Asian population. This was a two-part study. First, we conducted a retrospective 5-year review of autopsies performed in public mortuaries on young SCD victims. Second, we conducted a prospective 2-year study combining conventional autopsy investigations, molecular autopsy, and cardiac evaluation of the first-degree relatives of SCD victims. A panel of 35 genes implicated in SADS was analysed by next-generation sequencing. There were 289 SCD victims included in the 5-year review. Coronary artery disease was the major cause of death (35%); 40% were structural heart diseases and 25% were unexplained. These unexplained cases could include SADS-related conditions. In the 2-year prospective study, 21 SCD victims were examined: 10% had arrhythmogenic right ventricular cardiomyopathy, 5% had hypertrophic cardiomyopathy, and 85% had negative autopsy. Genetic analysis showed 29% with positive heterozygous genetic variants; six variants were novel. One third of victims had history of syncope, and 14% had family history of SCD. More than half of the 11 first-degree relatives who underwent genetic testing carried related genetic variants, and 10% had SADS-related clinical features. This pilot feasibility study shows the value of incorporating cardiac evaluation of surviving relatives and next-generation sequencing molecular autopsy into conventional forensic investigations in diagnosing young SCD victims in East Asian populations. The interpretation of genetic variants in the context of SCD is complicated and we recommend its analysis and reporting by qualified pathologists.

Functional and clinical relevance of novel mutations in a large cohort of patients with Cockayne syndrome

BackgroundCockayne syndrome (CS) is a rare, autosomal recessive multisystem disorder characterised by prenatal or postnatal growth failure, progressive neurological dysfunction, ocular and skeletal abnormalities and premature ageing. About half of...

Detection of mutations of the HNF1B gene in children with congenital anomalies of the kidney and urinary tract

Congenital anomalies of the kidney and urinary tract are caused by genetic alterations mostly unknown. Mutations in the gene that codes for hepatocyte nuclear factor 1B (HNF1B) are the most frequently described monogenic causes. Data are unknown in Chile and Latin America. To determine the presence of variants of the HNF1B gene in Chilean children with conge nital anomalies of the kidney and/or the urinary tract and their clinical characteristics. Descriptive study with children aged 10 months to 17 years, patients of the Calvo Mackenna Hospital Nephrology Unit, with cystic renal dysplasia, non cystic renal dysplasia/hypoplasia, horses hoe kidney between April and December 2016. HNF1B variants were determined by sequencing of exons 1, 2, 3 and 4 after DNA extraction and amplification. Restriction enzymes were used to define if the variants were homo or heterozygous. Direct family members of index cases were studied with sequencing of the affected exon. 32 patients were included, 43.75% males, median age 11 years. 65.6% of them had non-cystic renal dysplasia, 31.25% cystic renal dysplasia, and 3.15% hor seshoe kidney. In two patients (6.25%) the same heterozygous genetic variant was detected in exon 4, position 1027 (C1027T), not previously described. The study of relatives found the same variant in three out of five individuals, all without congenital nephro-urological anomalies. We confirmed the presence of a not previously described heterozygous genetic variant of the HNF1B gene. This work initiates the search for this type of mutations in our region which allows us to ap proach the knowledge of causality, determination of extrarenal involvement, and genetic counseling.

Novel Genetic Variants in BAG3 and TNNT2 in a Swedish Family with a History of Dilated Cardiomyopathy and Sudden Cardiac Death

Familial dilated cardiomyopathy is a rare cause of dilated cardiomyopathy (DCM), especially in childhood. Our aim was to describe the clinical course and the genetic variants in a family where the proband was a four-month-old infant presenting with respiratory problems due to DCM. In the family, there was a strong family history of DCM and sudden cardiac death in four generations. DNA was analyzed initially from the deceased girl using next-generation sequencing including 50 genes involved in cardiomyopathy. A cascade family screening was performed in the family after identification of the TNNT2 and the BAG3 variants in the proband. The first-degree relatives underwent clinical examination including biochemistry panel, cardiac ultrasound, Holter ECG, exercise stress test, and targeted genetic testing. The index patient presented with advanced DCM. After a severe clinical course, the baby had external left ventricular assist as a bridge to heart transplantation. 1.5 months after transplantation, the baby suffered sudden cardiac death (SCD) despite maximal treatment in the pediatric intensive care unit. The patient was shown to carry two heterozygous genetic variants in the TNNT2 gene [TNNT2 c.518G>A(p.Arg173Gln)] and BAG3 [BAG3 c.785C>T(p.Ala262Val)]. Two of the screened individuals (two females) appeared to carry both the familial variants. All the individuals carrying the TNNT2 variant presented with DCM, the two adult patients had mild or moderate symptoms of heart failure and reported palpitations but no syncope or presyncopal attacks prior to the genetic diagnosis. The female carriers of TNNT2 and BAG3 variants had more advanced DCM. In the family history, there were three additional cases of SCD due to DCM, diagnosed by autopsy, but no genetic analysis was possible in these cases. Our findings suggest that the variants in TNNT2 and BAG3 are associated with a high propensity to life-threatening cardiomyopathy presenting from childhood and young adulthood.

Characterization of a factor H mutation that perturbs the alternative pathway of complement in a family with membranoproliferative GN.

Complement C3 activation is a characteristic finding in membranoproliferative GN (MPGN). This activation can be caused by immune complex deposition or an acquired or inherited defect in complement regulation. Deficiency of complement factor H has long been associated with MPGN. More recently, heterozygous genetic variants have been reported in sporadic cases of MPGN, although their functional significance has not been assessed. We describe a family with MPGN and acquired partial lipodystrophy. Although C3 nephritic factor was shown in family members with acquired partial lipodystrophy, it did not segregate with the renal phenotype. Genetic analysis revealed a novel heterozygous mutation in complement factor H (R83S) in addition to known risk polymorphisms carried by individuals with MPGN. Patients with MPGN had normal levels of factor H, and structural analysis of the mutant revealed only subtle alterations. However, functional analysis revealed profoundly reduced C3b binding, cofactor activity, and decay accelerating activity leading to loss of regulation of the alternative pathway. In summary, this family showed a confluence of common and rare functionally significant genetic risk factors causing disease. Data from our analysis of these factors highlight the role of the alternative pathway of complement in MPGN.

The association of arylendosulfatase 1 (SULF1) gene polymorphism with recurrent miscarriage

One of the most common problems in reproductive medicine is recurrent miscarriage (RM). There is increasing evidence showing genetic susceptibility of women is an important risk factor in the occurrence of RM. In recent years, there is a growing interest in sulfate and its role in fetal development. A novel mechanism of SULF1 has been demonstrated for modifying the activities of some growth factors and signalling molecules that have major roles during embryogenesis. The aim of present study was to evaluate the association of SULF1 gene polymorphism (rs6990375 G > A) in Iranian patients with RM. We established a case-control study of 200 Iranian women: 100 patients with the history of two or more RM as cases and 100 healthy women with at least two cases of successful pregnancy and no history of miscarriage as controls. The polymorphism was examined by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. The genotypic analysis between case and controls showed significant differences (p-value = 0.000). Allelic analysis showed no significant correlation (Χ2 = 3.36, p-value = 0.066). The heterozygous genetic variant was significantly higher among healthy women (OR = 12.67, 95% CI = 6.47-24.79). Our data showed that rs6990375 polymorphism of SULF1 gene could be among one of the factors related to RM in Iranian women. Further evaluation of this polymorphism may be important and need further studies.