Genotypic spectrum of albinism in Mali.

Albinism is a phenotypically and genetically heterogeneous condition characterized by a variable degree of hypopigmentation and by ocular features leading to reduced visual acuity. Whereas numerous genotypic studies have been conducted throughout the world, very little is known about the genotypic spectrum of albinism in Africa and especially in sub-Saharan Western Africa. Here we report the analysis of all known albinism genes in a series a 23 patients originating from Mali. Four were diagnosed with OCA 1 (oculocutaneous albinism type 1), 17 with OCA 2, and two with OCA 4. OCA2 variant NM_000275.3:c.819_822delinsGGTC was most frequently encountered. Four novel variants were identified (two in TYR, two in OCA2). A deep intronic variant was found to alter splicing of the OCA2 RNA by inclusion of a pseudo exon. Of note, the OCA2 exon 7 deletion commonly found in eastern, central, and southern Africa was absent from this series. African patients with OCA 1 and OCA 4 had only been reported twice and once, respectively, in previous publications. This study constitutes the first report of the genotypic spectrum of albinism in a western sub-Saharan country.

Clinico-biological refinement of BCL11B-related disorder and identification of an episignature: A series of 20 unreported individuals.

PURPOSE: BCL11B-related disorder (BCL11B-RD) arises from rare genetic variants within the BCL11B gene, resulting in a distinctive clinical spectrum encompassing syndromic neurodevelopmental disorder, with or without intellectual disability, associated with facial features and impaired immune function. This study presents an in-depth clinico-biological analysis of 20 newly reported individuals with BCL11B-RD, coupled with a characterization of genome-wide DNA methylation patterns of this genetic condition. METHODS: Through an international collaboration, clinical and molecular data from 20 individuals were systematically gathered, and a comparative analysis was conducted between this series and existing literature. We further scrutinized peripheral blood DNA methylation profile of individuals with BCL11B-RD, contrasting them with healthy controls and other neurodevelopmental disorders marked by established episignature. RESULTS: Our findings unveil rarely documented clinical manifestations, notably including Rubinstein-Taybi-like facial features, craniosynostosis, and autoimmune disorders, all manifesting within the realm of BCL11B-RD. We refine the intricacies of T cell compartment alterations of BCL11B-RD, revealing decreased levels naive CD4+ T cells and recent thymic emigrants while concurrently observing an elevated proportion of effector-memory expressing CD45RA CD8+ T cells (TEMRA). Finally, a distinct DNA methylation episignature exclusive to BCL11B-RD is unveiled. CONCLUSION: This study serves to enrich our comprehension of the clinico-biological landscape of BCL11B-RD, potentially furnishing a more precise framework for diagnosis and follow-up of individuals carrying pathogenic BCL11B variant. Moreover, the identification of a unique DNA methylation episignature offers a valuable diagnosis tool for BCL11B-RD, thereby facilitating routine clinical practice by empowering physicians to reevaluate variants of uncertain significance within the BCL11B gene.

Ophthalmologic Phenotype-Genotype Correlations in Patients With Oculocutaneous Albinism Followed in a Reference Center.

Purpose: Albinism is a group of genetic disorders that includes several conditions related to a defect in melanin production. There is a broad phenotypic and genotypic variability between the different forms. The aim of this study was to assess the ophthalmologic characteristics according to patients' genotypes in a cohort followed in the Reference Center for oculocutaneous albinism (OCA) of Bordeaux University Hospital, France. Methods: A retrospective observational study was conducted in a cohort of patients with OCA seen in consultation in the ophthalmology department between 2017 and 2021 in whom a genetic analysis was performed. Results: In total, 127 patients with OCA were included in this study and matched with the results of the genetic analysis. In the population aged over 6 years, there was no statistical difference in binocular visual acuity between the OCA1, OCA2, and OCA4 forms (P = 0.27). There was difference in ametropia between the three forms (P = 0.003). A two-by-two comparison using the Bonferroni correction showed a significant difference in ametropia between the OCA2 and OCA4 forms (P = 0.007) and between the OCA1 and OCA2 forms (P = 0.0075). Regardless of the form, most patients (75.4%) had grade 4 foveal hypoplasia. There was no association between the grade of foveal hypoplasia and the gene involved (P = 0.87). Conclusions: We described a genotype-phenotype correlation for the three most represented forms of albinism in our cohort. This study allowed assessing the degree of visual deficiency in young children with OCA.

Unsuspected consequences of synonymous and missense variants in OCA2 can be detected in blood cell RNA samples of patients with albinism.

Oculocutaneous albinism type 2 (OCA2) is the second most frequent form of albinism and represents about 30% of OCA worldwide. As with all types of OCA, patients present with hypopigmentation of hair and skin, as well as severe visual abnormalities. We focused on a subgroup of 29 patients for whom genetic diagnosis was pending because at least one of their identified variants in or around exon 10 of OCA2 is of uncertain significance (VUS). By minigene assay, we investigated the effect of these VUS on exon 10 skipping and showed that not only intronic but also some synonymous variants can result in enhanced exon skipping. We further found that excessive skipping of exon 10 could be detected directly on blood samples of patients and of their one parent with the causal variant, avoiding invasive skin biopsies. Moreover, we show that variants, which result in lack of detectable OCA2 mRNA can be identified from blood samples as well, as shown for the most common OCA2 pathogenic missense variant c.1327G>A/p.(Val443Ile). In conclusion, blood cell RNA analysis allows testing the potential effect of any OCA2 VUS on transcription products. This should help to elucidate yet unsolved OCA2 patients and improve genetic counseling.

Monoallelic intragenic POU3F2 variants lead to neurodevelopmental delay and hyperphagic obesity, confirming the gene's candidacy in 6q16.1 deletions.

While common obesity accounts for an increasing global health burden, its monogenic forms have taught us underlying mechanisms via more than 20 single-gene disorders. Among these, the most common mechanism is central nervous system dysregulation of food intake and satiety, often accompanied by neurodevelopmental delay (NDD) and autism spectrum disorder. In a family with syndromic obesity, we identified a monoallelic truncating variant in POU3F2 (alias BRN2) encoding a neural transcription factor, which has previously been suggested as a driver of obesity and NDD in individuals with the 6q16.1 deletion. In an international collaboration, we identified ultra-rare truncating and missense variants in another ten individuals sharing autism spectrum disorder, NDD, and adolescent-onset obesity. Affected individuals presented with low-to-normal birth weight and infantile feeding difficulties but developed insulin resistance and hyperphagia during childhood. Except for a variant leading to early truncation of the protein, identified variants showed adequate nuclear translocation but overall disturbed DNA-binding ability and promotor activation. In a cohort with common non-syndromic obesity, we independently observed a negative correlation of POU3F2 gene expression with BMI, suggesting a role beyond monogenic obesity. In summary, we propose deleterious intragenic variants of POU3F2 to cause transcriptional dysregulation associated with hyperphagic obesity of adolescent onset with variable NDD.

KCNT2-Related Disorders: Phenotypes, Functional, and Pharmacological Properties.

OBJECTIVE: Pathogenic variants in KCNT2 are rare causes of developmental epileptic encephalopathy (DEE). We herein describe the phenotypic and genetic features of patients with KCNT2-related DEE, and the in vitro functional and pharmacological properties of KCNT2 channels carrying 14 novel or previously untested variants. METHODS: Twenty-five patients harboring KCNT2 variants were investigated: 12 were identified through an international collaborative network, 13 were retrieved from the literature. Clinical data were collected and included in a standardized phenotyping sheet. Novel variants were detected using exome sequencing and classified using ACMG criteria. Functional and pharmacological studies were performed by whole-cell electrophysiology in HEK-293 and SH-SY5Y cells. RESULTS: The phenotypic spectrum encompassed: (a) intellectual disability/developmental delay (21/22 individuals with available information), ranging from mild to severe/profound; (b) epilepsy (15/25); (c) neurological impairment, with altered muscle tone (14/22); (d) dysmorphisms (13/20). Nineteen pathogenic KCNT2 variants were found (9 new, 10 reported previously): 16 missense, 1 in-frame deletion of a single amino acid, 1 nonsense, and 1 frameshift. Among tested variants, 8 showed gain-of-function (GoF), and 6 loss-of-function (LoF) features when expressed heterologously in vitro. Quinidine and fluoxetine blocked all GoF variants, whereas loxapine and riluzole activated some LoF variants while blocking others. INTERPRETATION: We expanded the phenotypic and genotypic spectrum of KCNT2-related disorders, highlighting novel genotype-phenotype associations. Pathogenic KCNT2 variants cause GoF or LoF in vitro phenotypes, and each shows a unique pharmacological profile, suggesting the need for in vitro functional and pharmacological investigation to enable targeted therapies based on the molecular phenotype. ANN NEUROL 2023;94:332-349.

Hemidystonia with polymicrogyria is part of ATP1A3-related disorders.

INTRODUCTION: Pathogenic variants in ATP1A3 cause various phenotypes of neurological disorders, including alternating hemiplegia of childhood 2, CAPOS syndrome (cerebellar ataxia, areflexia, pes cavus, optic atrophy, and sensorineural hearing loss) and rapid-onset dystonia-parkinsonism (RDP). Early developmental and epileptic encephalopathy has also been reported. Polymicrogyria has recently been added to the phenotypic spectrum of ATP1A3-related disorders. CASE REPORT: We report here a male patient with early developmental delay who at 12 months presented dystonia of the right arm which evolved into hemidystonia at the age of 2. A cerebral MRI showed bilateral perisylvian polymicrogyria with intact basal ganglia. Whole-exome and whole-genome sequencing analyses identified a de novo new ATP1A3 missense variant (p.Arg914Lys) predicted pathogenic. Hemidystonia was thought not to be due to polymicrogyria, but rather a consequence of this variant. CONCLUSION: This case expands the phenotypic spectrum of ATP1A3-related disorders with a new variant associated with hemidystonia and polymicrogyria and thereby, suggests a clinical continuum between the different phenotypes of this condition.

The regional effect of serum hormone levels on cerebral blood flow in healthy nonpregnant women.

Sex hormones estrogen (EST) and progesterone (PROG) have received increased attention for their important physiological action outside of reproduction. While studies have shown that EST and PROG have significant impacts on brain function, their impact on the cerebrovascular system in humans remains largely unknown. To address this, we used a multi-modal magnetic resonance imaging (MRI) approach to investigate the link between serum hormones in the follicular phase and luteal phase of the menstrual cycle (MC) with measures of cerebrovascular function (cerebral blood flow [CBF]) and structure (intracranial artery diameter). Fourteen naturally cycling women were recruited and assessed at two-time points of their MC. CBF was derived from pseudo-continuous arterial spin labeling while diameters of the internal carotid and basilar artery was assessed using time of flight magnetic resonance angiography, blood samples were performed after the MRI. Results show that PROG and EST had opposing and spatially distinct effects on CBF: PROG correlated negatively with CBF in anterior brain regions (r = -.86, p < .01), while EST correlations were positive, yet weak and most prominent in posterior areas (r = .78, p < .01). No significant correlations between either hormone or intracranial artery diameter were observed. These results show that EST and PROG have opposing and regionally distinct effects on CBF and that this relationship is likely not due to interactions with large intracranial arteries. Considering that CBF in healthy women appears tightly linked to their current hormonal state, future studies should consider assessing MC-related hormone fluctuations in the design of functional MRI studies in this population.

Novel variants in the BLOC1S3 gene in patients presenting a mild form of Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) associates oculocutaneous albinism and systemic affections including platelet dense granules anomalies leading to bleeding diathesis and, depending on the form, pulmonary fibrosis, immunodeficiency, and/or granulomatous colitis. So far, 11 forms of autosomal recessive HPS caused by pathogenic variants in 11 different genes have been reported. We describe three HPS-8 consanguineous families with different homozygous pathogenic variants in BLOC1S3 (NM_212550.3), one of which is novel. These comprise two deletions leading to a reading frameshift (c.385_403del, c.338_341del) and one in frame deletion (c.444_467del). All patients have moderate oculocutaneous albinism and bleeding diathesis, but other HPS symptoms are not described. One patient diagnosed with HPS-8 suffered from lymphocyte-predominant Hodgkin lymphoma. The mild severity of HPS-8 is consistent with other HPS forms caused by variants in BLOC-1 complex coding genes (HPS-7, DTNBP1; HPS-9, BLOC1S6, HPS-11, BLOC1S5).

Triple diagnosis of Wiedemann-Steiner, Waardenburg and DLG3-related intellectual disability association found by WES: A case report.

BACKGROUND: The development of whole-exome sequencing (WES) and whole-genome sequencing (WGS) for clinical purposes now allows the identification of multiple pathogenic variants in patients with a rare disease. This occurs even when a single causative gene was initially suspected. We report the case of an 8-year-old patient with global developmental delays and dysmorphic features, with a possibly pathogenic variant in three distinct genes. METHODS: Trio-based exome sequencing was performed by IntegraGen SA (Evry, France), on an Illumina HiSeq4000 (Illumina, San Diego, CA, USA). Sanger sequencing was performed to confirm the variants that were found. RESULTS: WES showed the presence of three possibly deleterious variants: KMT2A: c.9068delA;p.Gln3023Argfs*3 de novo, PAX3: c.530C>G;p.Ala177Gly de novo and DLG3: c.127delG;p.Asp43Metfs*22 hemizygous inherited from the mother. KMT2A pathogenic variants are involved in Wiedemann-Steiner syndrome, and PAX3 is the gene responsible for Waardenburg syndrome. DLG3 variants have been described in a non-syndromic X-related intellectual disability. CONCLUSIONS: Considering the dysmorphic features and intellectual disability presented by this patient, these three variants were imputed as pathogenic and their association was considered responsible for his phenotype. Dual molecular diagnoses have already been found by WES in several cohorts with an average of diagnostic yield of 7%. This case demonstrates and reminds us of the importance of analyzing exomes rigorously and exhaustively because, in some cases (< 10%), it can explain superimposed traits or blended phenotypes.

Molecular characterization of a series of 990 index patients with albinism.

Albinism is a clinically and genetically heterogeneous disease characterized by variable degrees of hypopigmentation and by nystagmus, foveal hypoplasia, and chiasmatic misrouting of the optic nerves. The wide phenotypic heterogeneity impedes the establishment of phenotype-genotype correlations. To obtain a precise diagnosis, we screened the 19 known albinism genes in 990 index patients using targeted next-generation sequencing (NGS) and high-resolution comparative genomic hybridization. A molecular diagnosis was obtained in 72.32% of patients. A total of 243 new pathogenic variants were identified. Intragenic rearrangements represented 10.8% of all pathogenic alleles. NGS panel analysis allowed establishing a diagnosis for the rarest forms of the disease, which could not be diagnosed otherwise. Because of the clinical overlap between the different forms of the disease, diagnosis nowadays clearly relies on molecular grounds.

Clinico-molecular analysis of eleven patients with Hermansky-Pudlak type 5 syndrome, a mild form of HPS.

Hermansky-Pudlak syndrome (HPS), first described in 1959, is a rare form of syndromic oculocutaneous albinism associated with bleeding diathesis and in some cases pulmonary fibrosis and granulomatous colitis. All 10 HPS types are caused by defects in vesicle trafficking of lysosome-related organelles (LRO) proteins. The HPS5 protein associates with HPS3 and HPS6 to form the biogenesis of lysosome-related organelles complex-2 (BLOC-2). Here, we report the clinical and genetic data of 11 patients with HPS-5 analyzed in our laboratory. We report 11 new pathogenic variants. The 11 patients present with ocular features that are typical for albinism, with mild hypopigmentation, and with no other major complication, apart from a tendency to bleed. HPS-5 therefore appears as a mild form of HPS, which is often clinically undistinguishable from mild oculocutaneous or ocular forms of albinism. Molecular analysis is therefore required to establish the diagnosis of this mild HPS form, which has consequences in terms of prognosis and of clinical management of the patients.

Clinical and molecular findings in 39 patients with KBG syndrome caused by deletion or mutation of ANKRD11.

KBG syndrome, due to ANKRD11 alteration is characterized by developmental delay, short stature, dysmorphic facial features, and skeletal anomalies. We report a clinical and molecular study of 39 patients affected by KBG syndrome. Among them, 19 were diagnosed after the detection of a 16q24.3 deletion encompassing the ANKRD11 gene by array CGH. In the 20 remaining patients, the clinical suspicion was confirmed by the identification of an ANKRD11 mutation by direct sequencing. We present arguments to modulate the previously reported diagnostic criteria. Macrodontia should no longer be considered a mandatory feature. KBG syndrome is compatible with autonomous life in adulthood. Autism is less frequent than previously reported. We also describe new clinical findings with a potential impact on the follow-up of patients, such as precocious puberty and a case of malignancy. Most deletions remove the 5'end or the entire coding region but never extend toward 16q telomere suggesting that distal 16q deletion could be lethal. Although ANKRD11 appears to be a major gene associated with intellectual disability, KBG syndrome remains under-diagnosed. NGS-based approaches for sequencing will improve the detection of point mutations in this gene. Broad knowledge of the clinical phenotype is essential for a correct interpretation of the molecular results. © 2016 Wiley Periodicals, Inc.

African swine fever virus isolate, Georgia, 2007.

African swine fever (ASF) is widespread in Africa but is rarely introduced to other continents. In June 2007, ASF was confirmed in the Caucasus region of Georgia, and it has since spread to neighboring countries. DNA fragments amplified from the genome of the isolates from domestic pigs in Georgia in 2007 were sequenced and compared with other ASF virus (ASFV) isolates to establish the genotype of the virus. Sequences were obtained from 4 genome regions, including part of the gene B646L that encodes the p72 capsid protein, the complete E183L and CP204L genes, which encode the p54 and p30 proteins and the variable region of the B602L gene. Analysis of these sequences indicated that the Georgia 2007 isolate is closely related to isolates belonging to genotype II, which is circulating in Mozambique, Madagascar, and Zambia. One possibility for the spread of disease to Georgia is that pigs were fed ASFV-contaminated pork brought in on ships and, subsequently, the disease was disseminated throughout the region.