A novel missense variant in the ATPase domain of ATP8A2 and review of phenotypic variability of ATP8A2-related disorders caused by missense changes.

ATPase, class 1, type 8 A, member 2 (ATP8A2) is a P4-ATPase with a critical role in phospholipid translocation across the plasma membrane. Pathogenic variants in ATP8A2 are known to cause cerebellar ataxia, impaired intellectual development, and disequilibrium syndrome 4 (CAMRQ4) which is often associated with encephalopathy, global developmental delay, and severe motor deficits. Here, we present a family with two siblings born from a consanguineous, first-cousin union from Sudan presenting with global developmental delay, intellectual disability, spasticity, ataxia, nystagmus, and thin corpus callosum. Whole exome sequencing revealed a homozygous missense variant in the nucleotide binding domain of ATP8A2 (p.Leu538Pro) that results in near complete loss of protein expression. This is in line with other missense variants in the same domain leading to protein misfolding and loss of ATPase function. In addition, by performing diffusion-weighted imaging, we identified bilateral hyperintensities in the posterior limbs of the internal capsule suggesting possible microstructural changes in axon tracts that had not been appreciated before and could contribute to the sensorimotor deficits in these individuals.

Genetic diagnosis in Sudanese and Tunisian families with syndromic intellectual disability through exome sequencing.

BACKGROUND: Intellectual disability is a form of neurodevelopmental disorders that begin in childhood and is characterized by substantial intellectual difficulties as well as difficulties in conceptual, social, and practical areas of living. Several genetic and nongenetic factors contribute to its development; however, its most severe forms are generally attributed to single-gene defects. High-throughput technologies and data sharing contributed to the diagnosis of hundreds of single-gene intellectual disability subtypes. METHOD: We applied exome sequencing to identify potential variants causing syndromic intellectual disability in six Sudanese patients from four unrelated families. Data sharing through the Varsome portal corroborated the diagnosis of one of these patients and a Tunisian patient investigated through exome sequencing. Sanger sequencing validated the identified variants and their segregation with the phenotypes in the five studied families. RESULT: We identified three pathogenic/likely pathogenic variants in CCDC82, ADAT3, and HUWE1 and variants of uncertain significance in HERC2 and ATP2B3. The patients with the CCDC82 variants had microcephaly and spasticity, two signs absent in the two previously reported families with CCDC82-related intellectual disability. CONCLUSION: In conclusion, we report new patients with pathogenic mutations in the genes CCDC82, ADAT3, and HUWE1. We also highlight the possibility of extending the CCDC82-linked phenotype to include spastic paraplegia and microcephaly.

Novel variants causing megalencephalic leukodystrophy in Sudanese families.

Mutations in MLC1 cause megalencephalic leukoencephalopathy with subcortical cysts (MLC), a rare form of leukodystrophy characterized by macrocephaly, epilepsy, spasticity, and slow mental deterioration. Genetic studies of MLC are lacking from many parts of the world, especially in Sub-Saharan Africa. Genomic DNA was extracted for 67 leukodystrophic patients from 43 Sudanese families. Mutations were screened using the NGS panel testing 139 leukodystrophies and leukoencephalopathies causing genes (NextSeq500 Illumina). Five homozygous MLC1 variants were discovered in seven patients from five distinct families, including three consanguineous families from the same region of Sudan. Three variants were missense (c.971 T > G, p.Ile324Ser; c.344 T > C, p.Phe115Ser; and c.881 C > T, p.Pro294Leu), one duplication (c.831_838dupATATCTGT, p.Ser280Tyrfs*8), and one synonymous/splicing-site mutation (c.762 C > T, p.Ser254). The segregation pattern was consistent with autosomal recessive inheritance. The clinical presentation and brain MRI of the seven affected patients were consistent with the diagnosis of MLC1. Due to the high frequency of distinct MLC1 mutations found in our leukodystrophic Sudanese families, we analyzed the coding sequence of MLC1 gene in 124 individuals from the Sudanese genome project in comparison with the 1000-genome project. We found that Sudan has the highest proportion of deleterious variants in MLC1 gene compared with other populations from the 1000-genome project.

An identical-by-descent novel splice-donor variant in PRUNE1 causes a neurodevelopmental syndrome with prominent dystonia in two consanguineous Sudanese families.

PRUNE1 is linked to a wide range of neurodevelopmental and neurodegenerative phenotypes. Multiple pathogenic missense and stop-gain PRUNE1 variants were identified in its DHH and DHHA2 phosphodiesterase domains. Conversely, a single splice alteration was previously reported. We investigated five patients from two unrelated consanguineous Sudanese families with an inherited severe neurodevelopmental disorder using whole-exome sequencing coupled with homozygosity mapping, segregation, and haplotype analysis. We identified a founder haplotype transmitting a homozygous canonical splice-donor variant (NM_021222.3:c.132+2T > C) in intron 2 of PRUNE1 segregated with the phenotype in all the patients. This splice variant possibly results in an in-frame deletion in the DHH domain or premature truncation of the protein. The phenotypes of the affected individuals showed phenotypic similarities characterized by remarkable pyramidal dysfunction and prominent extrapyramidal features (severe dystonia and bradykinesia). In conclusion, we identified a novel founder variant in PRUNE1 and corroborated abnormal splicing events as a disease mechanism in PRUNE1-related disorders. Given the phenotypes' consistency coupled with the founder effect, canonical and cryptic PRUNE1 splice-site variants should be carefully evaluated in patients presenting with prominent dystonia and pyramidal dysfunction.

A children's epilepsy diagnosis aid: Development and early validation using a Bayesian approach.

INTRODUCTION: The diagnosis of epilepsy in children is difficult and misdiagnosis rates can be as much as 36%. Diagnosis in all countries is essentially clinical, based on asking a series of questions and interpreting the answers. Doctors experienced enough to do this are either scarce or absent in very many parts of the world so there is a need to develop a diagnostic aid to help less-experienced doctors or non-physician health workers (NPHWs) do this. We used a Bayesian approach to determine the most useful questions to ask based on their likelihood ratios (LR), and incorporated these into a Children's Epilepsy Diagnosis Aid (CEDA). METHODS: Ninety-six consecutive new referrals with possible epilepsy aged under 10 years attending a pediatric neurology clinic in Khartoum were included. Initially, their caregivers were asked 65 yes/no questions by a medical officer, then seen by pediatric neurologist and the diagnosis of epilepsy (E), not epilepsy (N), or uncertain (U) was made. The LR was calculated and then we selected the variables with the highest and lowest LRs which are the most informative at differentiating epilepsy from non-epilepsy. An algorithm, (CEDA), based on the most informative questions was constructed and tested on a new sample of 47 consecutive patients with a first attendance of possible epilepsy. We calculated the sensitivity and specificity for CEDA in the diagnosis of epilepsy. RESULTS: Sixty-nine (79%) had epilepsy and 18 (21%) non-epilepsy giving pre-test odds of having epilepsy of 3.83. Eleven variables with the most informative LRs formed the diagnostic aid (CEDA). The pre-test odds and algorithm were used to determine the probability of epilepsy diagnosis in a subsequent sample of 47 patients. There were 36 patients with epilepsy and 11 with nonepileptic conditions. The sensitivity of CEDA was 100% with specificity of 97% and misdiagnosis 8.3%. CONCLUSION: Children's Epilepsy Diagnosis Aid has the potential to improve pediatric epilepsy diagnosis and therefore management and is particularly likely to be useful in the many situations where access to epilepsy specialists is limited. The algorithm can be presented as a smartphone application or used as a spreadsheet on a computer.

Intelligence quotient (IQ) among children with epilepsy: National epidemiological study - Sudan.

BACKGROUND: Many studies of selected groups of children with epilepsy have demonstrated an association between epilepsy and cognitive deficits. The aim of this study was to assess the intellectual skills of children with epilepsy and to investigate the influence of gender, age at seizure onset, type of epilepsy, antiepileptic drug used, and control of epilepsy on their intellectual function. METHODS: This is a descriptive prospective study in which one hundred and eighty-seven patients at school age (6-14 years) were recruited. Epilepsy was classified using the International League Against Epilepsy (ILAE) Commission on Classification and Terminology 2005-2009 report. An intelligence quotient (IQ) test was conducted to all patients using Stanford-Binet Fifth Edition (SB5)/Arabic version. RESULTS: Eighty-eight (47.1%) patients had an average score on Full Scale IQ (FSIQ), 44 (23.5%) had low average, whereas 18 (9.6%) had borderline impaired or delayed score. In the nonverbal IQ (NVIQ) score, the majority 84 (44.9%) had average score. The performance of the patients in the nonverbal score is better than in the verbal score, which was found to be statistically significant (P-value = 0.01). The FSIQ score was negatively affected by younger age at onset of epilepsy, polytherapy, and uncontrolled seizures. CONCLUSIONS: Most of children with epilepsy had an average FSIQ; uncontrolled seizure had worse effect on overall FSIQ and memory. Interventions to support children with epilepsy should focus on epilepsy management and school psychosocial domains.

Overlap of polymicrogyria, hydrocephalus, and Joubert syndrome in a family with novel truncating mutations in ADGRG1/GPR56 and KIAA0556.

Genetic mutations associated with brain malformations can lead to a spectrum of severity and it is often difficult to determine whether there are additional pathogenic variants contributing to the phenotype. Here, we present a family affected by a severe brain malformation including bilateral polymicrogyria, hydrocephalus, patchy white matter signal changes, and cerebellar and pontine hypoplasia with elongated cerebellar peduncles leading to the molar tooth sign. While the malformation is reminiscent of bilateral frontoparietal polymicrogyria (BFPP), the phenotype is more severe than previously reported and also includes features of Joubert syndrome (JBTS). Via exome sequencing, we identified homozygous truncating mutations in both ADGRG1/GPR56 and KIAA0556, which are known to cause BFPP and mild brain-specific JBTS, respectively. This study shows how two independent mutations can interact leading to complex brain malformations.

Classification and management of epilepsy and epileptic syndromes in a cohort of 202 school children- a 2 year follow up study- Sudan.

BACKGROUND: In this paper, seizure types, and epilepsy syndromes are elucidated as per ILAE (2010) classification. A brief outline of the antiepileptic drug regimens used and the outcome of seizure control in a two -year period is presented. The applicability of the ILAE classification in resource limited countries has been revisited. METHODS: This is a descriptive prospective study, in which 202 patients were enrolled. The Cohort group was seen and evaluated by a pediatric neurologist at the Pediatric neurology Outpatients Department (OPD). Epilepsy was classified using the International League Against Epilepsy (ILAE) classification (2005-2009) report. All patients had an Electroencephalogram (EEG) at the start of the study, and this was repeated as deemed appropriate. Brain imaging (MRI) was done to patients when indicated. Treatment decisions were made by pediatric neurologists. Outcomes were categorized into four groups: fully recovered, well controlled, partially controlled and uncontrolled. RESULTS: The mean age is 10.5 + 2.7 years. Male to female ratio was 1.7: 1. Thirty five (17.3%) patients had generalized onset seizures, 46(22.8%) had focal onset seizures, 104(51.5%) had a specific epilepsy syndrome, and 17(8.4%) patients were unclassified. 170 (84.2%) patients were on mono-therapy on their initial visit, 30(14.8%) were on two Antiepileptic Drugs (AEDs) while two (1.0%) patients were on poly-therapy. After 2 years; 155(76.7%) patients were on mono-therapy, 36(17.8%) on two AEDs while ten were (4.0%) on polytherapy. One eighty (88.2%) patients were controlled. Fifteen (7.4%) of them were off medication after being seizure free for 2 years. Twenty (9.8%) have partial control, while two (1.0%) patients were uncontrolled. Patients with focal epilepsy, those on polytherapy and those with abnormal imaging had poor prognosis. CONCLUSIONS: The ILAE classification can be used in resource limited countries. Childhood epilepsies have a good prognosis provided they are well classified and treated.

Impact of PYROXD1 deficiency on cellular respiration and correlations with genetic analyses of limb-girdle muscular dystrophy in Saudi Arabia and Sudan.

Next-generation sequencing is commonly used to screen for pathogenic mutations in families with Mendelian disorders, but due to the pace of discoveries, gaps have widened for some diseases between genetic and pathophysiological knowledge. We recruited and analyzed 16 families with limb-girdle muscular dystrophy (LGMD) of Arab descent from Saudi Arabia and Sudan who did not have confirmed genetic diagnoses. The analysis included both traditional and next-generation sequencing approaches. Cellular and metabolic studies were performed on Pyroxd1 siRNA C2C12 myoblasts and controls. Pathogenic mutations were identified in eight of the 16 families. One Sudanese family of Arab descent residing in Saudi Arabia harbored a homozygous c.464A>G, p.Asn155Ser mutation in PYROXD1, a gene recently reported in association with myofibrillar myopathy and whose protein product reduces thiol residues. Pyroxd1 deficiency in murine C2C12 myoblasts yielded evidence for impairments of cellular proliferation, migration, and differentiation, while CG10721 (Pyroxd1 fly homolog) knockdown in Drosophila yielded a lethal phenotype. Further investigations indicated that Pyroxd1 does not localize to mitochondria, yet Pyroxd1 deficiency is associated with decreased cellular respiration. This study identified pathogenic mutations in half of the LGMD families from the cohort, including one in PYROXD1. Developmental impairments were demonstrated in vitro for Pyroxd1 deficiency and in vivo for CG10721 deficiency, with reduced metabolic activity in vitro for Pyroxd1 deficiency.

Expanding the phenome and variome of skeletal dysplasia.

PURPOSE: To describe our experience with a large cohort (411 patients from 288 families) of various forms of skeletal dysplasia who were molecularly characterized. METHODS: Detailed phenotyping and next-generation sequencing (panel and exome). RESULTS: Our analysis revealed 224 pathogenic/likely pathogenic variants (54 (24%) of which are novel) in 123 genes with established or tentative links to skeletal dysplasia. In addition, we propose 5 genes as candidate disease genes with suggestive biological links (WNT3A, SUCO, RIN1, DIP2C, and PAN2). Phenotypically, we note that our cohort spans 36 established phenotypic categories by the International Skeletal Dysplasia Nosology, as well as 18 novel skeletal dysplasia phenotypes that could not be classified under these categories, e.g., the novel C3orf17-related skeletal dysplasia. We also describe novel phenotypic aspects of well-known disease genes, e.g., PGAP3-related Toriello-Carey syndrome-like phenotype. We note a strong founder effect for many genes in our cohort, which allowed us to calculate a minimum disease burden for the autosomal recessive forms of skeletal dysplasia in our population (7.16E-04), which is much higher than the global average. CONCLUSION: By expanding the phenotypic, allelic, and locus heterogeneity of skeletal dysplasia in humans, we hope our study will improve the diagnostic rate of patients with these conditions.

Case report of a novel homozygous splice site mutation in PLA2G6 gene causing infantile neuroaxonal dystrophy in a Sudanese family.

BACKGROUND: Infantile neuroaxonal dystrophy (INAD) is a rare hereditary neurological disorder caused by mutations in PLA2G6. The disease commonly affects children below 3 years of age and presents with delay in motor skills, optic atrophy and progressive spastic tetraparesis. Studies of INAD in Africa are extremely rare, and genetic studies from Sub Saharan Africa are almost non-existent. CASE PRESENTATION: Two Sudanese siblings presented, at ages 18 and 24 months, with regression in both motor milestones and speech development and hyper-reflexia. Brain MRI showed bilateral and symmetrical T2/FLAIR hyperintense signal changes in periventricular areas and basal ganglia and mild cerebellar atrophy. Whole exome sequencing with confirmatory Sanger sequencing were performed for the two patients and healthy family members. A novel variant (NM_003560.2 c.1427 + 2 T > C) acting on a splice donor site and predicted to lead to skipping of exon 10 was found in PLA2G6. It was found in a homozygous state in the two patients and homozygous reference or heterozygous in five healthy family members. CONCLUSION: This variant has one very strong (loss of function mutation) and three supporting evidences for its pathogenicity (segregation with the disease, multiple computational evidence and specific patients' phenotype). Therefore this variant can be currently annotated as "pathogenic". This is the first study to report mutations in PLA2G6 gene in patients from Sudan.

The differential effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on seizure frequency in patients with drug-resistant epilepsy - A randomized, double-blind, placebo-controlled trial.

OBJECTIVES: The omega-3 (n-3) fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are known to play an important role in maintenance and modulation of neuronal functions. There is evidence that omega-3 fatty acids may have anticonvulsant effects. The effect of DHA and EPA on seizure rate in patients with drug-resistant epilepsy (DRE) was investigated. METHODS: A double-blind, randomized, placebo-controlled clinical trial included ninety-nine (n = 99) subjects with DRE, aged 5-16 years (n = 85) and 17-45 years (n = 14). After randomization, subjects were given two, four, or six capsules per day of DHA (417.8 mg DHA and 50.8 mg EPA/capsule, n = 33), EPA (385.6 mg EPA and 81.2 mg DHA/capsule, n = 33), or placebo (high oleic acid sunflower oil, n = 33) for one year. The primary endpoint was the effect of treatment on rate of seizure. Random-effects negative binomial regression models were fitted to model the patients' total count of seizures per month. The treatment effects on seizure incidence rate ratio (IRR) were tested after controlling for the covariate effects of gender, age, rate of seizure per week at enrollment, type of seizure, and number of antiepileptic drug (AED) combinations used at enrollment. RESULTS: Fifty-nine subjects (n = 59) completed the study (59.6%). The average number of seizures per month were 9.7 ±â€¯1.2 in the EPA group, 11.7 ±â€¯1.5 in the DHA group, and 16.6 ±â€¯1.5 in the placebo group. Age, gender, and seizure-type adjusted seizure IRRs of the EPA and DHA groups compared with the placebo group were 0.61 (CI = 0.42-0.88, p = 0.008, 42% reduction) and 0.67 (CI = 0.46-1.0, p = 0.04, 39% reduction), respectively. There was no difference in IRR between the EPA and DHA groups (p = 0.56). Both treatment groups had a significantly higher number of seizure-free days compared with the placebo group (p < 0.05). SIGNIFICANCE: This study demonstrates that EPA and DHA are effective in reducing seizure frequency in patients with DRE.

A novel missense variant in the ATPase domain of ATP8A2 and review of phenotypic variability of ATP8A2-related disorders caused by missense changes.

ATPase, class 1, type 8A, member 2 (ATP8A2) is a P4-ATPase with a critical role in phospholipid translocation across the plasma membrane. Pathogenic variants in ATP8A2 are known to cause cerebellar ataxia, mental retardation, and disequilibrium syndrome 4 (CAMRQ4) which is often associated with encephalopathy, global developmental delay, and severe motor deficits. Here, we present a family with two siblings presenting with global developmental delay, intellectual disability, spasticity, ataxia, nystagmus, and thin corpus callosum. Whole exome sequencing revealed a homozygous missense variant in the nucleotide binding domain of ATP8A2 (p.Leu538Pro) that results in near complete loss of protein expression. This is in line with other missense variants in the same domain leading to protein misfolding and loss of ATPase function. In addition, by performing diffusion-weighted imaging, we identified bilateral hyperintensities in the posterior limbs of the internal capsule suggesting possible microstructural changes in axon tracts that had not been appreciated before and could contribute to the sensorimotor deficits in these individuals.

Bi-allelic PRRT2 variants may predispose to Self-limited Familial Infantile Epilepsy.

Heterozygous PRRT2 variants are frequently implicated in Self-limited Infantile Epilepsy, whereas homozygous variants are so far linked to severe presentations including developmental and epileptic encephalopathy, movement disorders, and intellectual disability. In a study aiming to explore the genetics of epilepsy in the Sudanese population, we investigated several families including a consanguineous family with three siblings diagnosed with self-limited infantile epilepsy. We evaluated both dominant and recessive inheritance using whole exome sequencing and genomic arrays. We identified a pathogenic homozygous splice-site variant in the first intron of PRRT2 [NC_000016.10(NM_145239.3):c.-65-1G > A] that segregated with the phenotype in this family. This work taps into the genetics of epilepsy in an underrepresented African population and suggests that the phenotypes of homozygous PRRT2 variants may include milder epilepsy presentations without movement disorders.

Clinical phenotyping and genetic diagnosis of a large cohort of Sudanese families with hereditary spinocerebellar degenerations.

Hereditary spinocerebellar degenerations (SCDs) is an umbrella term that covers a group of monogenic conditions that share common pathogenic mechanisms and include hereditary spastic paraplegia (HSP), cerebellar ataxia, and spinocerebellar ataxia. They are often complicated with axonal neuropathy and/or intellectual impairment and overlap with many neurological conditions, including neurodevelopmental disorders. More than 200 genes and loci inherited through all modes of Mendelian inheritance are known. Autosomal recessive inheritance predominates in consanguineous communities; however, autosomal dominant and X-linked inheritance can also occur. Sudan is inhabited by genetically diverse populations, yet it has high consanguinity rates. We used next-generation sequencing, genotyping, bioinformatics analysis, and candidate gene approaches to study 90 affected patients from 38 unrelated Sudanese families segregating multiple forms of SCDs. The age-at-onset in our cohort ranged from birth to 35 years; however, most patients manifested childhood-onset diseases (the mean and median ages at onset were 7.5 and 3 years, respectively). We reached the genetic diagnosis in 63% and possibly up to 73% of the studied families when considering variants of unknown significance. Combining the present data with our previous analysis of 25 Sudanese HSP families, the success rate reached 52-59% (31-35/59 families). In this article we report candidate variants in genes previously known to be associated with SCDs or other phenotypically related monogenic disorders. We also highlight the genetic and clinical heterogeneity of SCDs in Sudan, as we did not identify a major causative gene in our cohort, and the potential for discovering novel SCD genes in this population.

A novel homozygous mutation in TRAPPC9 gene causing autosomal recessive non-syndromic intellectual disability.

BACKGROUND: The etiology of intellectual disabilities is diverse and includes both genetic and environmental factors. The genetic causes of intellectual disabilities range from chromosomal aberrations to single gene disorders. The TRAPPC9 gene has been reported to cause autosomal recessive forms of intellectual disabilities in 56 patients from consanguineous and non-consanguineous families around the world. METHODS: We analyzed two siblings with intellectual disability, microcephaly and delayed motor and speech development from a consanguineous Sudanese family. Genomic DNA was screened for mutations using NGS panel (NextSeq500 Illumina) testing 173 microcephaly associated genes in the Molecular Genetics service in Robert Debre hospital in Paris, France. RESULTS: A novel homozygous mutation (NM_031466.7 (TRAPPC9):c.2288dup, p. (Val764Glyfs*7) in exon 14 of TRAPPC9 gene was found in the two patients. The mutation was predicted to cause nonsense mediated decay (NSMD) using SIFT prediction tool. The variant has not been found in either gnomAD or Exac databases. Both parents were heterozygous (carriers) to the mutation. CONCLUSION: This is the first study to report patients with TRAPPC9-related disorder from Sub-Saharan Africa.

Case Report: A New Family With Pontocerebellar Hypoplasia 10 From Sudan.

Pontocerebellar hypoplasia type 10 (PCH10) is a very rare autosomal recessive neurodegenerative disease characterized by intellectual disability, microcephaly, severe developmental delay, pyramidal signs, mild cerebellar atrophy, and white matter changes in the brain, as shown by magnetic resonance imaging (MRI). The disease has been described in only twenty-one patients from ten Turkish families with a founder missense pathogenic variant in the CLP1 gene involved in tRNA processing and maturation. We analyzed three siblings from a consanguineous Sudanese family who presented with intellectual disability, dysmorphic features, developmental delay, regression of milestones, microcephaly, epilepsy, extrapyramidal signs, mild pontine, and cerebellar atrophy. We identified through whole-exome sequencing the same pathogenic variant (c.419G>A; p(Arg140His) reported before in all Turkish families. Our study extends the phenotypes of PCH10 and reports for the first time cases with PCH10 of non-Turkish origin.

Methylation of alpha-synuclein in a Sudanese cohort.

BACKGROUND: Several studies suggested a significant role of epigenetic changes, including alterations in miRNA, histone modifications, and DNA methylation of α-synuclein (SNCA) in Parkinson's disease (PD) pathogenicity. As of yet, only very few studies have been carried out in this field in Africa and none in Sudan. MATERIALS AND METHODS: We collected DNA from 172 Sudanese individuals (90 cases, 82 controls) who donated saliva for DNA extraction (mean age of onset: 40.6 ± 22.4 years). A family history of PD was evident in 64 patients. DNA preparation and bisulfite sequencing of SNCAintron1 was performed as described earlier. RESULTS: Of the fourteen analyzed CpGs of SNCAintron1, CpGs 16-23 were hypomethylated in PD (P-value ranged from 0.023 to 0.003). P-values improved, when sporadic cases were excluded from the analysis. CONCLUSION: We identified the presence of a specific pattern of DNA methylation in a young Sudanese cohort of familial PD, which confirms the importance of the methylation of SNCAintron1 for PD. This phenomenon appears to be independent of ethnicity, the impact of environmental factors, drug history, or familial clustering.

Pathogenic Variants in ABHD16A Cause a Novel Psychomotor Developmental Disorder With Spastic Paraplegia.

Introduction: Hereditary spastic paraplegia is a clinically and genetically heterogeneous neurological entity that includes more than 80 disorders which share lower limb spasticity as a common feature. Abnormalities in multiple cellular processes are implicated in their pathogenesis, including lipid metabolism; but still 40% of the patients are undiagnosed. Our goal was to identify the disease-causing variants in Sudanese families excluded for known genetic causes and describe a novel clinico-genetic entity. Methods: We studied four patients from two unrelated consanguineous Sudanese families who manifested a neurological phenotype characterized by spasticity, psychomotor developmental delay and/or regression, and intellectual impairment. We applied next-generation sequencing, bioinformatics analysis, and Sanger sequencing to identify the genetic culprit. We then explored the consequences of the identified variants in patients-derived fibroblasts using targeted-lipidomics strategies. Results and Discussion: Two homozygous variants in ABHD16A segregated with the disease in the two studied families. ABHD16A encodes the main brain phosphatidylserine hydrolase. In vitro, we confirmed that ABHD16A loss of function reduces the levels of certain long-chain lysophosphatidylserine species while increases the levels of multiple phosphatidylserine species in patient's fibroblasts. Conclusion: ABHD16A loss of function is implicated in the pathogenesis of a novel form of complex hereditary spastic paraplegia.