Influence of autozygosity on common disease risk across the phenotypic spectrum.

Autozygosity is associated with rare Mendelian disorders and clinically relevant quantitative traits. We investigated associations between the fraction of the genome in runs of homozygosity (FROH) and common diseases in Genes & Health (n = 23,978 British South Asians), UK Biobank (n = 397,184), and 23andMe. We show that restricting analysis to offspring of first cousins is an effective way of reducing confounding due to social/environmental correlates of FROH. Within this group in G&H+UK Biobank, we found experiment-wide significant associations between FROH and twelve common diseases. We replicated associations with type 2 diabetes (T2D) and post-traumatic stress disorder via within-sibling analysis in 23andMe (median n = 480,282). We estimated that autozygosity due to consanguinity accounts for 5%-18% of T2D cases among British Pakistanis. Our work highlights the possibility of widespread non-additive genetic effects on common diseases and has important implications for global populations with high rates of consanguinity.

Functional Selectivity in Cytokine Signaling Revealed Through a Pathogenic EPO Mutation.

Cytokines are classically thought to stimulate downstream signaling pathways through monotonic activation of receptors. We describe a severe anemia resulting from a homozygous mutation (R150Q) in the cytokine erythropoietin (EPO). Surprisingly, the EPO R150Q mutant shows only a mild reduction in affinity for its receptor but has altered binding kinetics. The EPO mutant is less effective at stimulating erythroid cell proliferation and differentiation, even at maximally potent concentrations. While the EPO mutant can stimulate effectors such as STAT5 to a similar extent as the wild-type ligand, there is reduced JAK2-mediated phosphorylation of select downstream targets. This impairment in downstream signaling mechanistically arises from altered receptor dimerization dynamics due to extracellular binding changes. These results demonstrate how variation in a single cytokine can lead to biased downstream signaling and can thereby cause human disease. Moreover, we have defined a distinct treatable form of anemia through mutation identification and functional studies.

Network of large pedigrees reveals social practices of Avar communities.

From AD 567-568, at the onset of the Avar period, populations from the Eurasian Steppe settled in the Carpathian Basin for approximately 250 years1. Extensive sampling for archaeogenomics (424 individuals) and isotopes, combined with archaeological, anthropological and historical contextualization of four Avar-period cemeteries, allowed for a detailed description of the genomic structure of these communities and their kinship and social practices. We present a set of large pedigrees, reconstructed using ancient DNA, spanning nine generations and comprising around 300 individuals. We uncover a strict patrilineal kinship system, in which patrilocality and female exogamy were the norm and multiple reproductive partnering and levirate unions were common. The absence of consanguinity indicates that this society maintained a detailed memory of ancestry over generations. These kinship practices correspond with previous evidence from historical sources and anthropological research on Eurasian Steppe societies2. Network analyses of identity-by-descent DNA connections suggest that social cohesion between communities was maintained via female exogamy. Finally, despite the absence of major ancestry shifts, the level of resolution of our analyses allowed us to detect genetic discontinuity caused by the replacement of a community at one of the sites. This was paralleled with changes in the archaeological record and was probably a result of local political realignment.

Genetics of Inborn Errors of Immunity in highly consanguineous Middle Eastern and North African populations.

Consanguineous marriages in Middle Eastern and North African (MENA) countries are deeply-rooted tradition and highly prevalent resulting into increased prevalence of autosomal recessive diseases including Inborn Errors of Immunity (IEIs). Molecular genetic testing is an important diagnostic tool for IEIs since it provides a definite diagnosis, genotype-phenotype correlation, and guide therapy. In this review, we will discuss the current state and challenges of genomic and variome studies in MENA region populations, as well as the importance of funding advanced genome projects. In addition, we will review the MENA underlying molecular genetic defects of over 2457 patients published with the common IEIs, where autosomal recessive mode of inheritance accounts for 76% of cases with increased prevalence of combined immunodeficiency diseases (50%). The efforts made in the last three decades in terms of international collaboration and of in situ capacity building in MENA region countries led to the discovery of more than 150 novel genes involved in IEIs. Expanding sequencing studies within the MENA will undoubtedly be a unique asset for the IEI genetics which can advance research, and support precise genomic diagnostics and therapeutics.

A dynastic elite in monumental Neolithic society.

The nature and distribution of political power in Europe during the Neolithic era remains poorly understood1. During this period, many societies began to invest heavily in building monuments, which suggests an increase in social organization. The scale and sophistication of megalithic architecture along the Atlantic seaboard, culminating in the great passage tomb complexes, is particularly impressive2. Although co-operative ideology has often been emphasised as a driver of megalith construction1, the human expenditure required to erect the largest monuments has led some researchers to emphasize hierarchy3-of which the most extreme case is a small elite marshalling the labour of the masses. Here we present evidence that a social stratum of this type was established during the Neolithic period in Ireland. We sampled 44 whole genomes, among which we identify the adult son of a first-degree incestuous union from remains that were discovered within the most elaborate recess of the Newgrange passage tomb. Socially sanctioned matings of this nature are very rare, and are documented almost exclusively among politico-religious elites4-specifically within polygynous and patrilineal royal families that are headed by god-kings5,6. We identify relatives of this individual within two other major complexes of passage tombs 150 km to the west of Newgrange, as well as dietary differences and fine-scale haplotypic structure (which is unprecedented in resolution for a prehistoric population) between passage tomb samples and the larger dataset, which together imply hierarchy. This elite emerged against a backdrop of rapid maritime colonization that displaced a unique Mesolithic isolate population, although we also detected rare Irish hunter-gatherer introgression within the Neolithic population.

Evaluating drug targets through human loss-of-function genetic variation.

Naturally occurring human genetic variants that are predicted to inactivate protein-coding genes provide an in vivo model of human gene inactivation that complements knockout studies in cells and model organisms. Here we report three key findings regarding the assessment of candidate drug targets using human loss-of-function variants. First, even essential genes, in which loss-of-function variants are not tolerated, can be highly successful as targets of inhibitory drugs. Second, in most genes, loss-of-function variants are sufficiently rare that genotype-based ascertainment of homozygous or compound heterozygous 'knockout' humans will await sample sizes that are approximately 1,000 times those presently available, unless recruitment focuses on consanguineous individuals. Third, automated variant annotation and filtering are powerful, but manual curation remains crucial for removing artefacts, and is a prerequisite for recall-by-genotype efforts. Our results provide a roadmap for human knockout studies and should guide the interpretation of loss-of-function variants in drug development.

Increased homozygosity due to endogamy results in fitness consequences in a human population.

Recessive alleles have been shown to directly affect both human Mendelian disease phenotypes and complex traits. Pedigree studies also suggest that consanguinity results in increased childhood mortality and adverse health phenotypes, presumably through penetrance of recessive mutations. Here, we test whether the accumulation of homozygous, recessive alleles decreases reproductive success in a human population. We address this question among the Namibian Himba, an endogamous agro-pastoralist population, who until very recently practiced natural fertility. Using a sample of 681 individuals, we show that Himba exhibit elevated levels of "inbreeding," calculated as the fraction of the genome in runs of homozygosity (FROH). Many individuals contain multiple long segments of ROH in their genomes, indicating that their parents had high kinship coefficients. However, we do not find evidence that this is explained by first-cousin consanguinity, despite a reported social preference for cross-cousin marriages. Rather, we show that elevated haplotype sharing in the Himba is due to a bottleneck, likely in the past 60 generations. We test whether increased recessive mutation load results in observed fitness consequences by assessing the effect of FROH on completed fertility in a cohort of postreproductive women (n = 69). We find that higher FROH is significantly associated with lower fertility. Our data suggest a multilocus genetic effect on fitness driven by the expression of deleterious recessive alleles, especially those in long ROH. However, these effects are not the result of consanguinity but rather elevated background identity by descent.

SRD5A3 is required for converting polyprenol to dolichol and is mutated in a congenital glycosylation disorder.

N-linked glycosylation is the most frequent modification of secreted and membrane-bound proteins in eukaryotic cells, disruption of which is the basis of the congenital disorders of glycosylation (CDGs). We describe a new type of CDG caused by mutations in the steroid 5alpha-reductase type 3 (SRD5A3) gene. Patients have mental retardation and ophthalmologic and cerebellar defects. We found that SRD5A3 is necessary for the reduction of the alpha-isoprene unit of polyprenols to form dolichols, required for synthesis of dolichol-linked monosaccharides, and the oligosaccharide precursor used for N-glycosylation. The presence of residual dolichol in cells depleted for this enzyme suggests the existence of an unexpected alternative pathway for dolichol de novo biosynthesis. Our results thus suggest that SRD5A3 is likely to be the long-sought polyprenol reductase and reveal the genetic basis of one of the earliest steps in protein N-linked glycosylation.

Paediatric diabetes subtypes in a consanguineous population: a single-centre cohort study from Kurdistan, Iraq.

AIMS/HYPOTHESIS: Monogenic diabetes is estimated to account for 1-6% of paediatric diabetes cases in primarily non-consanguineous populations, while the incidence and genetic spectrum in consanguineous regions are insufficiently defined. In this single-centre study we aimed to evaluate diabetes subtypes, obtain the consanguinity rate and study the genetic background of individuals with syndromic and neonatal diabetes in a population with a high rate of consanguinity. METHODS: Data collection was carried out cross-sectionally in November 2021 at the paediatric diabetic clinic, Dr Jamal Ahmad Rashed Hospital, in Sulaimani, Kurdistan, Iraq. At the time of data collection, 754 individuals with diabetes (381 boys) aged up to 16 years were registered. Relevant participant data was obtained from patient files. Consanguinity status was known in 735 (97.5%) participants. Furthermore, 12 families of children with neonatal diabetes and seven families of children with syndromic diabetes consented to genetic testing by next-generation sequencing. Prioritised variants were evaluated using the American College of Medical Genetics and Genomics guidelines and confirmed by Sanger sequencing. RESULTS: A total of 269 of 735 participants (36.5%) with known consanguinity status were offspring of consanguineous families. An overwhelming majority of participants (714/754, 94.7%) had clinically defined type 1 diabetes (35% of them were born to consanguineous parents), whereas only eight (1.1%) had type 2 diabetes (38% consanguineous). Fourteen (1.9%) had neonatal diabetes (50% consanguineous), seven (0.9%) had syndromic diabetes (100% consanguineous) and 11 (1.5%) had clinically defined MODY (18% consanguineous). We found that consanguinity was significantly associated with syndromic diabetes (p=0.0023) but not with any other diabetes subtype. The genetic cause was elucidated in ten of 12 participants with neonatal diabetes who consented to genetic testing (homozygous variants in GLIS3 [sibling pair], PTF1A and ZNF808 and heterozygous variants in ABCC8 and INS) and four of seven participants with syndromic diabetes (homozygous variants in INSR, SLC29A3 and WFS1 [sibling pair]). In addition, a participant referred as syndromic diabetes was diagnosed with mucolipidosis gamma and probably has type 2 diabetes. CONCLUSIONS/INTERPRETATION: This unique single-centre study confirms that, even in a highly consanguineous population, clinically defined type 1 diabetes is the prevailing paediatric diabetes subtype. Furthermore, a pathogenic cause of monogenic diabetes was identified in 83% of tested participants with neonatal diabetes and 57% of participants with syndromic diabetes, with most variants being homozygous. Causative genes in our consanguineous participants were markedly different from genes reported from non-consanguineous populations and also from those reported in other consanguineous populations. To correctly diagnose syndromic diabetes in consanguineous populations, it may be necessary to re-evaluate diagnostic criteria and include additional phenotypic features such as short stature and hepatosplenomegaly.

Bi-allelic variants in HCRT cause autosomal recessive narcolepsy.

Narcolepsy with cataplexy is a complex disease with both genetic and environmental risk factors. To gain further insight into the homozygous HCRT-related narcolepsy, we present a case series of five patients from two consanguineous families, each harboring a novel homozygous variant of HCRT c.17_18del. All affected individuals exhibited severe cataplexy accompanied by narcolepsy symptoms during infancy. Additionally, cataplexy symptoms improved or disappeared in the majority of patients over time. Pathogenic variants in HCRT cause autosomal recessive narcolepsy with cataplexy. Genetic testing of the HCRT gene should be conducted in specific subgroups of narcolepsy, particularly those with early onset, familial cases, and a predominantly cataplexy phenotype.

2020 Curt Stern Award address: a more perfect clinical genome-how consanguineous populations contribute to the medical annotation of the human genome.

This article is based on the address given by the author at the 2020 virtual meeting of the American Society of Human Genetics (ASHG) on October 26, 2020. The video of the original address can be found at the ASHG website.

The landscape of autosomal-recessive pathogenic variants in European populations reveals phenotype-specific effects.

The number and distribution of recessive alleles in the population for various diseases are not known at genome-wide-scale. Based on 6,447 exome sequences of healthy, genetically unrelated Europeans of two distinct ancestries, we estimate that every individual is a carrier of at least 2 pathogenic variants in currently known autosomal-recessive (AR) genes and that 0.8%-1% of European couples are at risk of having a child affected with a severe AR genetic disorder. This risk is 16.5-fold higher for first cousins but is significantly more increased for skeletal disorders and intellectual disabilities due to their distinct genetic architecture.

Monoallelic and bi-allelic variants in NCDN cause neurodevelopmental delay, intellectual disability, and epilepsy.

Neurochondrin (NCDN) is a cytoplasmatic neural protein of importance for neural growth, glutamate receptor (mGluR) signaling, and synaptic plasticity. Conditional loss of Ncdn in mice neural tissue causes depressive-like behaviors, impaired spatial learning, and epileptic seizures. We report on NCDN missense variants in six affected individuals with variable degrees of developmental delay, intellectual disability (ID), and seizures. Three siblings were found homozygous for a NCDN missense variant, whereas another three unrelated individuals carried different de novo missense variants in NCDN. We assayed the missense variants for their capability to rescue impaired neurite formation in human neuroblastoma (SH-SY5Y) cells depleted of NCDN. Overexpression of wild-type NCDN rescued the neurite-phenotype in contrast to expression of NCDN containing the variants of affected individuals. Two missense variants, associated with severe neurodevelopmental features and epilepsy, were unable to restore mGluR5-induced ERK phosphorylation. Electrophysiological analysis of SH-SY5Y cells depleted of NCDN exhibited altered membrane potential and impaired action potentials at repolarization, suggesting NCDN to be required for normal biophysical properties. Using available transcriptome data from human fetal cortex, we show that NCDN is highly expressed in maturing excitatory neurons. In combination, our data provide evidence that bi-allelic and de novo variants in NCDN cause a clinically variable form of neurodevelopmental delay and epilepsy, highlighting a critical role for NCDN in human brain development.

Inborn Errors of Immunity in Jordan: First Report from a Tertiary Referral Center.

PURPOSE: Inborn errors of immunity (IEI) are a heterogeneous group of diseases with variable clinical phenotypes. This study was conducted to describe the epidemiology, clinical presentations, treatment, and outcome of IEI in Jordanian children. METHODS: A retrospective data analysis was conducted for children under 15 years diagnosed with IEI from the pediatric Allergy, Immunology, and Rheumatology Division-based registry at Queen Rania Children's Hospital, Amman, Jordan, between 2010 and 2022. RESULTS: A total of 467 patients, 263 (56.3%) males and 204 (43.7%) females, were diagnosed with IEI. The mean age at symptom onset was 18 months (1 week to 144 months), a positive family history of IEI was reported in 43.5%, and the consanguinity rate was 47.9%. The most common IEI category was immunodeficiencies affecting cellular and humoral immunity at 33.2%, followed by predominantly antibody deficiencies at 16.9%. The overall median diagnostic delay (range) was 6 (0-135) months; patients with a positive family history of IEI had a statistically significant shorter diagnostic delay. Pulmonary and gastrointestinal clinical features were the most common at 55.2% and 45.6%, respectively. The overall mortality was 33.2%; the highest rate was reported in severe combined immunodeficiency at 56.2%. CONCLUSIONS: The high minimal estimated IEI prevalence at 16.2/100,000 Jordanian children compared to the regional and worldwide data, with the diversities in clinical presentation and distribution of IEI categories in our cohort point to unique features of IEI in Jordanian children, call for national registry establishment, regional and international collaborative networks.

Genomic testing identifies monogenic causes in patients with very early-onset inflammatory bowel disease: a multicenter survey in an Iranian cohort.

Patients with very early-onset inflammatory bowel disease (VEO-IBD) may present because of underlying monogenic inborn errors of immunity (IEI). Strong differences have been observed in the causes of monogenic IBD among ethnic populations. This multicenter study was carried out on 16 Iranian patients with VEO-IBD. We reviewed clinical and basic immunologic evaluation including flow cytometry and immunoglobulin levels. All patients underwent clinical whole exome sequencing (WES). Sixteen patients (8 females and 8 males) with a median age of 43.5 months were enrolled. The median age at the onset of symptoms was 4 months. Most patients (12, 75%) had consanguineous parents. Chronic non-bloody diarrhea (13, 81.3%) and perianal diseases including perianal abscess (6, 37.5%), anal fissure (6, 37.5%), or anal fistula (2, 12.5%) were the most common manifestations. WES identified a spectrum of genetic variants in 13 patients (81.3%): IL10RB (6, 37.5%), MVK (3, 18.8%), and CASP8, SLC35C1, G6PC3, and IKBKB in 1 patient, respectively. In 3 patients (18.7%), no variant was identified. Flow cytometry identified a spectrum of abnormalities that helped to assess the evidence of genetic diagnosis. At the end of the survey, 3 (18.8%) patients were deceased. This high rate of monogenic defects with a broad spectrum of genes reiterates the importance of investigating IEI in patients with infantile-onset IBD.

Expanding Access to Noninvasive Prenatal Diagnosis for Monogenic Conditions to Consanguineous Families.

BACKGROUND: Cell-free fetal DNA exists within the maternal bloodstream during pregnancy and provides a means for noninvasive prenatal diagnosis (NIPD). Our accredited clinical service offers definitive NIPD for several autosomal recessive (AR) and X-linked conditions using relative haplotype dosage analysis (RHDO). RHDO involves next-generation sequencing (NGS) of thousands of common single nucleotide polymorphism (SNPs) surrounding the gene of interest in the parents and an affected or unaffected offspring to conduct haplotype phasing of the high- and low-risk alleles. NGS is carried out in parallel on the maternal cell-free DNA, and fetal inheritance is predicted using sensitive dosage calculations performed at sites where the parental genotypes differ. RHDO is not currently offered to consanguineous couples owing to the shared haplotype between parents. Here we test the expansion of RHDO for AR monogenic conditions to include consanguineous couples. METHODS: The existing sequential probability ratio test analysis pipeline was modified to apply to SNPs where both parents are heterozygous for the same genotype. Quality control thresholds were developed using 33 nonconsanguineous cases. The performance of the adapted RHDO pipeline was tested on 8 consanguineous cases. RESULTS: The correct fetal genotype was predicted by our revised RHDO approach in all conclusive cases with known genotypes (n = 5). Haplotype block classification accuracies of 94.5% and 93.9% were obtained for the nonconsanguineous and consanguineous case cohorts, respectively. CONCLUSIONS: Our modified RHDO pipeline correctly predicts the genotype in fetuses from consanguineous families, allowing the potential to expand access to NIPD services for these families.

Severe manifestation of Rauch-Azzarello syndrome associated with biallelic deletion of CTNND2.

CTNND2 encodes δ-catenin, a component of an adherens junction complex, and plays an important role in neuronal structure and function. To date, only heterozygous loss-of-function CTNND2 variants have been associated with mild neurodevelopmental delay and behavioral anomalies, a condition, which we named Rauch-Azzarello syndrome. Here, we report three siblings of a consanguineous family of Syrian descent with a homozygous deletion encompassing the last 19 exons of CTNND2 predicted to disrupt the transcript. All presented with severe neurodevelopmental delay with absent speech, profound motor delay, stereotypic behavior, microcephaly, short stature, muscular hypotonia with lower limb hypertonia, and variable eye anomalies. The parents and the fourth sibling were heterozygous carriers of the deletion and exhibited mild neurodevelopmental impairment resembling that of the previously described heterozygous individuals. The present study unveils a severe manifestation of CTNND2-associated Rauch-Azzarello syndrome attributed to biallelic loss-of-function aberrations, clinically distinct from the already described mild presentation of heterozygous individuals. Furthermore, we demonstrate novel clinical features in homozygous individuals that have not been reported in heterozygous cases to date.

Autozygome-guided exome-first study in a consanguineous cohort with early-onset retinal disease uncovers an isolated RIMS2 phenotype and a retina-enriched RIMS2 isoform.

Leber congenital amaurosis (LCA) and early-onset retinal degeneration (EORD) are inherited retinal diseases (IRD) characterized by early-onset vision impairment. Herein, we studied 15 Saudi families by whole exome sequencing (WES) and run-of-homozygosity (ROH) detection via AutoMap in 12/15 consanguineous families. This revealed (likely) pathogenic variants in 11/15 families (73%). A potential founder variant was found in RPGRIP1. Homozygous pathogenic variants were identified in known IRD genes (ATF6, CRB1, CABP4, RDH12, RIMS2, RPGRIP1, SPATA7). We established genotype-driven clinical reclassifications for ATF6, CABP4, and RIMS2. Specifically, we observed isolated IRD in the individual with the novel RIMS2 variant, and we found a retina-enriched RIMS2 isoform conserved but not annotated in mouse. The latter illustrates potential different phenotypic consequences of pathogenic variants depending on the particular tissue/cell-type specific isoforms they affect. Lastly, a compound heterozygous genotype in GUCY2D in one non-consanguineous family was demonstrated, and homozygous variants in novel candidate genes ATG2B and RUFY3 were found in the two remaining consanguineous families. Reporting these genes will allow to validate them in other IRD cohorts. Finally, the missing heritability of the two unsolved IRD cases may be attributed to variants in non-coding regions or structural variants that remained undetected, warranting future WGS studies.

Multi-gene panel sequencing in highly consanguineous families and patients with congenital forms of skeletal dysplasias.

Skeletal dysplasias (SKDs) are a heterogeneous group of more than 750 genetic disorders characterized by abnormal development, growth, and maintenance of bones or cartilage in the human skeleton. SKDs are often caused by variants in early patterning genes and in many cases part of multiple malformation syndromes and occur in combination with non-skeletal phenotypes. The aim of this study was to investigate the underlying genetic cause of congenital SKDs in highly consanguineous Pakistani families, as well as in sporadic and familial SKD cases from India using multigene panel sequencing analysis. Therefore, we performed panel sequencing of 386 bone-related genes in 7 highly consanguineous families from Pakistan and 27 cases from India affected with SKDs. In the highly consanguineous families, we were able to identify the underlying genetic cause in five out of seven families, resulting in a diagnostic yield of 71%. Whereas, in the sporadic and familial SKD cases, we identified 12 causative variants, corresponding to a diagnostic yield of 44%. The genetic heterogeneity in our cohorts was very high and we were able to detect various types of variants, including missense, nonsense, and frameshift variants, across multiple genes known to cause different types of SKDs. In conclusion, panel sequencing proved to be a highly effective way to decipher the genetic basis of SKDs in highly consanguineous families as well as sporadic and or familial cases from South Asia. Furthermore, our findings expand the allelic spectrum of skeletal dysplasias.

The utility of exome sequencing in diagnosing pediatric neurodevelopmental disorders in a highly consanguineous population.

Exome sequencing (ES) has been utilized in diagnosing children with neurodevelopmental manifestations, this study aimed to investigate the utility of ES in children within a highly consanguineous population that presented with neurodevelopmental complaints. A retrospective chart review was performed for 405 children with neurodevelopmental complaints who have had ES and were evaluated in multiple centers in the United Arab Emirates over a four-year period. Within the cohort of 405 children, consanguinity was reported in 35% (144/405). The primary clinical presentations were developmental delay/cognitive impairment, distinctive facial features, hypotonia, seizures, and weakness. The diagnostic yield was 57% (231/405). Novel variants were identified in 54% (125/231) of positive cases. Within the positive cases, specific treatment was available in 6% (13/231) and copy number variants (CNV) were reported in 3% (8/231) of cases. In eight children, variants in genes that have not yet been linked to human disease that could potentially be the cause of the observed phenotype "candidate genes" were identified. ES was utilized effectively within this cohort with a high diagnostic yield and through the identification of novel gene variants, CNVs, candidate genes and secondary findings as well as the alteration of the treatment plan in cases where treatment was available.