Homozygous Variant Research Articles

Genetic variants in patients with multiple arterial aneurysms

PurposeThe aim of this study was to identify causal genetic variants in patients with multiple arterial aneurysms.MethodsFrom a total cohort of 3107 patients diagnosed with an arterial aneurysm from 2006 to 2016, patients with known hereditary connective tissue diseases, vasculitis, or other arterial pathologies (n = 918) were excluded. Of the remaining cohort (n = 2189), patients with at least 4 aneurysms at different arterial locations (n = 143) were included. Nine blood samples of respective patients were available and derived from the institutional vascular biomaterial bank, and analyzed by whole exome sequencing (WES). Possible candidate variants were selected based on in silico predictions: (I) Truncating variants or (II) Variants that were classified as likely pathogenic (SIFT score < 0.05 or PolyPhen score > 0.9) and with low (< 0.001) or unknown gnomAD allele frequency. The human genome databases GeneCards and MalaCards were used to correlate the variants with regard to possible associations with vascular diseases.ResultsA total of 24 variants in 23 different genes associated with vascular diseases were detected in the cohort. One patient with eight aneurysms was heterozygous for a variant in SMAD3, for which pathogenic variants are phenotypically associated with Loeys-Dietz syndrome 3. A heterozygous variant in TNXB was found in a patient with five aneurysms. Homozygous or compound heterozygous pathogenic variants in this gene are associated with Ehlers-Danlos syndrome (classical-like). Another patient with six aneurysms carried two heterozygous TET2 variants together with a heterozygous PPM1D variant. Pathogenic variants in these genes are associated with clonal hematopoiesis of indeterminate potential (CHIP), a known risk factor for cardiovascular disease.ConclusionAll nine patients in this study carried variants in genes associated with vascular diseases. Current knowledge of the specific variants is insufficient to classify them as pathogenic at the present time, underlining the need for a better understanding of the consequences of genetic variants. WES should be considered for patients with multiple arterial aneurysms to detect germline variants and to improve clinical management for the individual and family members.

A Novel Homozygous Variant in CPLANE1 Gene in a Patient with Developmental Deficits

Background: Oral-facial-digital syndrome (OFDS) type 6 is a rare subtype of Joubert syndrome characterized by orofacial anomalies and polydactyly with neurological features of Joubert syndrome. This rare syndrome is divided into thirteen subtypes, all of which demonstrate autosomal recessive inheritance, except for OFDS type 1 which demonstrates X-linked dominant inheritance. Case Presentation: A 19-year-old man with mild developmental delay was brought to a rural community clinic, as he had become irritable and angry, in the recent past. There was no history of prior medical conditions. In view of orofacial anomalies, and developmental deficits, a genetic analysis was requested. Karyotype analysis revealed a normal male karyotype (46,XY) in all 30 metaphase spreads analyzed. No numerical or structural chromosomal abnormalities were observed. Clinical exome sequencing and chromosomal microarray detected a variant of uncertain significance in exon 5 of CPLANE1 gene c.365T&amp;gt;G (p.Val122Gly) leading to substitution of Glycine for Valine. This was confirmed by Sanger sequencing. Parents were heterozygous, and the unaffected sibling was homozygous for the wild-type allele. This variant has not been reported earlier in the mutation databases or gnomAD. Runs of homozygosity (ROH) analysis showed a 3.2 Mb ROH around the CPLANE1 gene in the proband, which was absent in both parents and the unaffected sibling. Conclusion: We find a novel homozygous mutation in the CPLANE1 gene in a patient of non-consanguineous parentage with atypical orofacial features. This suggests that potentially deleterious, rare variants may occur in the heterozygous state in the population. Hence, sequencing of population samples might help understand the genetic epidemiology of rare syndromes.

A case of peeling skin syndrome type 1 with novel CDSN gene variation successfully treated with upadacitinib.

Peeling skin syndrome type 1 (PSS1) is an autosomal recessive genodermatosis caused by the CDSN gene loss-of-function mutation and characterized by widespread superficial skin peeling and erythroderma with unbearable pruritus. Because of its ultra-rarity and unclear mechanism, this rare disease has no established treatment regimen. Herein, we reported a Chinese woman who presented with congenital generalized pruritic erythroderma and exfoliation, notable for significantly elevated IgE levels. The whole exome sequencing identified an unpublished homozygous variant (c.295C>T, p.Gln99*) in the CDSN gene, confirming the diagnosis of PSS1. Immunohistochemistry analysis of the affected skin confirmed the lack of corneodesmosin expression, revealed the overexpression of T helper 2 (Th2)-related cytokines harboring interleukin (IL) 4 and IL-13. After Janus kinase 1 (JAK1) inhibitor upadacitinib administration, both the patient's skin rashes and itching symptoms were significantly alleviated. Our work expanded the PSS1-related CDSN gene mutation spectrums, substantiated the hypothesis regarding the overexpression of Th2-related cytokines, and uncovered the important role of JAK1 underlying PSS1. JAK1 signaling may dominate the pathogenesis in PSS1 and represent a potential therapeutic target.

Cost-saving approach with screening of selected variants in genetic diagnosis in Turkish pediatric familial Mediterranean fever patients: a single center longitudinal study.

The aim of this study was to investigate whether a short exon screening consisting of selected variants could confirm the diagnosis in patients with a preliminary diagnosis of familial Mediterranean fever (FMF), thus providing a cost-saving alternative to a comprehensive MEditerranean FeVer (MEFV) gene sequence analysis test. This observational study on pediatric patients focused on clinically suspected FMF cases without prior genetic analysis. Participants met the Turkish pediatric FMF criteria. They underwent short exon screening for M694V, M680I, V726A, and E148Q variants. Those who were heterozygous or negative on short exon screening received further MEFV gene sequence analysis. The study involved 1557 patients. Pathogenic variants in both alleles of the MEFV gene were found in 611 patients (39.2%), and a high-penetrance variant in heterozygosity or an E148Q variant on the other allele was found in 643 patients (41.3%). A further 189 patients (12.1%) had one or two E148Q variants. Short-exon screening was negative in 114 patients (7.6%). Of the 876 patients who underwent MEFV gene sequence analysis, additional variants were found in 72 of the 762 initially heterozygous patients. Of the 114 initially negative patients, 34 had homozygous or compound heterozygous variants, and 74 had heterozygous variants. Ultimately, only 6 patients yielded negative results in the MEFV gene sequence analysis. The short exon screening for common MEFV mutations offers a practical and cost-saving alternative to comprehensive MEFV gene sequence analysis in populations with a high prevalence of FMF.

9378 Knockdown Of The Cdh2 Gene In Zebrafish Determines Its Role In Terminal Hormone Differentiation

Abstract Disclosure: B.V. Fernandes: None. C. MacRae: None. L.R. Carvalho: None. M. Junqueira: None. Introduction: Congenital hypopituitarism (CH) is characterized by the deficiency of one or more pituitary hormones. Whole exome sequencing (WES) has allowed the identification of novel/rare variants in genetic diseases. Among CH patients, 85% lack a molecular diagnosis. WES approach in a patients born to consanguineous parents identified the homozygous variant (c.865G&amp;gt;A, p. Val289Ile) in the CDH2 gene that produce N-Cadherin protein responsible for cell-cell adhesion. This variant was predicted as likely pathogenic allelic variant by ACMG criteria was found in a patient with GH, TSH, ACTH, LF/FSH deficiencies associated with an ectopic neurohypophysis and pituitary hypoplasia. CDH2 analysis in a cohort of 219 patients with CH, followed in a single Brazilian center, identified 3 unrelated families with heterozygous variants and incomplete penetrance where 2 were novel, in addition to the p. Val289Ile. The deleterious effect of the homozygous variant on cell adhesion properties was confirmed in permanent transfection assays in L1 fibroblast cell lines. To determine the role of the cdh2 gene in pituitary development and hormone production and secretion, we selected zebrafish as an animal model due to its 75% genetic homology with humans. Knockout of cdh2 using Crispr/cas9 genomic edition resulted in 85% lethality of animals at 48 hours post-fertilization (hpf), precluding analysis of its role during pituitary development. Objective: To produce a cdh2 knockdown in zebrafish for phenotypic and molecular analysis. Materials and Methods: The pET28B-RfxCas13d-His plasmid was transformed, linearized, and followed by in vitro transcription to produce Cas13 mRNA. Three guide RNAs targeting the cdh2 gene were designed to guide Cas13 to the target. The Cas13/RNA guide complex was injected into single-cell embryos, and phenotypic analyses were performed under a stereomicroscope until 96 hpf. To evaluate cdh2, prop1, pit1 and gh gene expression by RT-PCR, embryos were collected at 24, 48, 72, and 96 hpf. Results: Knockdown animals exhibited microcephaly, cardiac edema, and microphthalmia during embryonic development. CDH2 expression was decreased by 75% in the first 24 hours of life and began to recover by 48 hours, gradually increasing until 96 hpf when it equaled to WT. gh expression was statistically decreased at 48h compared to WT, with an increased gh expression similar to cdh2 increasing reaching similar WT levels by 96 hpf. There was no statistically significant difference in prop1 and pit1 expression compared to WT in the analyzed periods. Conclusion: The cdh2 knockdown in zebrafish using Cas13 enzyme was effective with cdh2 decreased expression by 75% presenting a phenotype similar to the knockout model. Decreased gh expression at 48h suggests an important role of cdh2 in hormonal terminal differentiation, which should be corroborated by analysis of other hormone expressions. Presentation: 6/2/2024

7096 Variants in WASHC3, a component of the WASH complex, cause distinctive facial dysmorphism, short stature, and variable neurodevelopmental abnormalities

Abstract Disclosure: Y. Jee: None. J. Lui: None. D. Marafi: None. Z. Xia: None. R. Bhatia: None. E. Zhou: None. I. Herman: None. A.G. Temnycky: None. P. Whalen: None. G. Elliot: None. E. Leschek: None. R. Wijngaard: None. R. Beek: None. A. Vreugd: None. M. De Vries: None. C. Karnebeek: None. M. Oud: None. T. Markello: None. K. Barnes: None. H. Alrohaif: None. H.H. Freeze: None. W. Gahl: None. M. Malicdan: None. J. Posey: None. J. Lupski: None. J. Baron: None. Genetic defects that impair growth plate chondrogenesis can result in a spectrum of phenotypes, ranging from skeletal dysplasia to mild short stature, sometimes accompanied by syndromic features. However, the genetic underpinnings of impaired skeletal growth often remain elusive. In our study, we investigated three unrelated families with short stature (height standard deviation score z &amp;lt; -2), distinctive facies (down-slanting eyes, low set ears, high arched palate, and short neck), and various neurodevelopmental abnormalities (from leaning difficulties to low intelligence quotient). In these families, exome sequencing (ES) identified rare, predicted-pathogenic variant alleles in WASHC3 that segregated with the phenotype. WASHC3 is a component of the WASH complex, which is involved in endosome receptor recycling. In the first family, a de novo-dominant missense variant (p.L69F) impaired WASHC3 participation in the WASH complex. This variant led to altered PTH1R endosomal trafficking, resulting in diminished PTH1R signaling and impairing growth plate chondrocyte hypertrophic differentiation, providing a likely explanation for the short stature. Knockdown of other WASH complex components (WASH1, SWIP, Strumpellin) also diminished PTH1R signaling, confirming the importance of an intact WASH complex. In the second and third families, a homozygous variant in the start codon (p.M1?) markedly reduced WASHC3 protein expression by approximately 75%. In conclusion, our findings strongly suggest that the WASH complex is required for normal skeletal growth and that, consequently, genetic abnormalities impairing the function of the WASH complex (WASHopathy) cause short stature as well as distinctive facies and variable neurodevelopmental abnormalities. These effects are likely mediated through disruptions in endosomal receptor trafficking. This new pathological information sheds light on the molecular basis of impaired longitudinal bone growth. Presentation: 6/3/2024

7238 A rare cause of primary ovarian failure in an adolescent due to a genetic mutation in mitochondrial poly-A-polymerase (mTPAP) mRNA

Abstract Disclosure: J. Epstein: None. S. Veera: None. J. Pappas: None. B.C. Shah: None. Primary ovarian insufficiency (POI) is a dysfunction or loss of ovarian follicles with associated amenorrhea. While most causes are idiopathic, approximately 15% of POI cases are due to single gene or chromosomal abnormalities, such as X chromosome abnormalities. Many of these nuclear genes encode for proteins that function within the mitochondria. Mitochondrial disorders affect tissues with high energy demand, such as the neurological, skeletal, cardiac, and endocrine systems. Furthermore, mature ovaries have a relatively higher concentration of mitochondria, which play a role in cellular respiration along with steroidogenesis. Mutations that disrupt these pathways can therefore lead to ovarian dysfunction. We present a case of a 17-year-old female with concern for primary amenorrhea. She underwent pubarche at age 12 years and thelarche at 14 years, with slowed progression. Height Z score was -1.61 and weight Z score was -0.41. Lab work at presentation was significant for LH 18.6 IU/L (N 2.4-12.6 IU/L), FSH 43.9 IU/L (N 1.1-9.6 IU/L), low estradiol &amp;lt;2.5 pg/mL (N 30-100 pg/mL), low total testosterone 8.3 ng/dL (N 15-31 ng/dL), unremarkable HbA1C, cortisol, thyroid levels, and a 46 XX karyotype. Pelvic ultrasound showed small ovarian volumes with a 1.9 cc right ovary, 1.5 cc left ovary consistent with lack of hormonal stimulation, and uterus length of 4.9 cm (N &amp;gt; 4 cm) consistent with early hormonal stimulation. She was started on transdermal estrogen replacement. Past medical history included stable pericardial effusion, episodes of supraventricular tachycardia, pre-cataracts, speech delays, mild learning disabilities, spastic diplegia, progressive gait abnormalities, ligamentous laxity, and recurrent patellar dislocations requiring multiple orthopedic limb surgeries. Family history was significant for parental consanguinity as first cousins. As the etiology of the POI remained unknown, genetic testing was completed. Whole exome sequencing (WES) revealed a homozygous pathogenic variant in the MTPAP gene: p.(Leu495Arg) (CTG&amp;gt;CGG): c.1484 T&amp;gt;G in exon 9 on chromosome 10p11.23. MTPAP, also known as SPAX4, TENT6, or PAPD1, is a nuclear-encoded polymerase involved in synthesizing the 3’ poly(A) tail of mitochondrial transcripts as well as in mRNA degradation. She was diagnosed with autosomal recessive MTPAP-related neurodevelopmental and movement disorder. Monogenic disorders affecting mitochondrial function are rare causes of POI. A high index of suspicion should be raised when a constellation of neurological, musculoskeletal, and cardiac problems co-exist. WES can be a very useful tool for uncovering rare genetic disorders. Further studies are needed to clarify details of organ specific mitochondrial dysfunction and possible therapeutics in individuals affected with MTPAP-related neurodevelopmental and movement disorders. Presentation: 6/1/2024

Comprehensive molecular and clinical findings in 29 patients with multi-locus imprinting disturbance

BackgroundMulti-locus imprinting disturbance (MLID) with methylation defects in various differentially methylated regions (DMRs) has recently been identified in approximately 150 cases with imprinting disorders (IDs), and deleterious variants have been found in genes related to methylation maintenance of DMRs, such as those encoding proteins constructing the subcortical maternal complex (SCMC), in a small fraction of patients and/or their mothers. However, integrated methylation analysis for DMRs and sequence analysis for MLID-causative genes in MLID cases and their mothers have been performed only in a single study focusing on Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) phenotypes.ResultsOf 783 patients with various IDs we have identified to date, we examined a total of 386 patients with confirmed epimutation and 71 patients with epimutation or uniparental disomy. Consequently, we identified MLID in 29 patients with epimutation confirmed by methylation analysis for multiple ID-associated DMRs using pyrosequencing and/or methylation-specific multiple ligation-dependent probe amplification. MLID was detected in approximately 12% of patients with BWS phenotype and approximately 5% of patients with SRS phenotype, but not in patients with Kagami-Ogata syndrome, Prader-Willi syndrome, or Angelman syndrome phenotypes. We next conducted array-based methylation analysis for 78 DMRs and whole-exome sequencing in the 29 patients, revealing hypomethylation-dominant aberrant methylation patterns in various DMRs of all the patients, eight probably deleterious variants in genes for SCMC in the mothers of patients, and one homozygous deleterious variant in ZNF445 in one patient. These variants did not show gene-specific methylation disturbance patterns. Clinically, neurodevelopmental delay and/or intellectual developmental disorder (ND/IDD) was observed in about half of the MLID patients, with no association with the identified methylation disturbance patterns and genetic variants. Notably, seven patients with BWS phenotype were conceived by assisted reproductive technology (ART).ConclusionsThe frequency of MLID was 7.5% (29/386) in IDs caused by confirmed epimutation. Furthermore, we revealed diverse patterns of hypomethylation-dominant methylation defects, nine deleterious variants, ND/IDD complications in about half of the MLID patients, and a high frequency of MLID in ART-conceived patients.

6408 Familial Hypoparathyroidism With Elevated Parathyroid Hormone Due To A PTH Mutation Responsive To Teriparatide

Abstract Disclosure: N. Mukhtar: None. B. Alghamdi: None. M. Alswailem: None. A.S. Alzahrani: None. Introduction: Apart from vitamin D disorders, causes of congenital hypocalcemia (HypoCa) include genetic defects causing familial hypoparathyroidism (FH), and defects in PTH receptor or its signalling pathway (PTH resistance). The former is typically characterized by low plasma PTH and the latter by elevated PTH levels. In this report, we describe a family with FH but with significant elevation of functionally inactive PTH due to a PTH mutation. We also show a positive therapeutic impact of recombinant human PTH (teriparatide) therapy on HypoCa in one of these siblings who was not well controlled on calcitriol and calcium replacement. Case description: The proband is a 34-year-old lady who has history of chronic HypoCa since birth with several admissions for severe HypoCa and recurrent seizures during childhood. She and her three brothers (a 32-year-old male twin and an 18-year-old male) were diagnosed to have Pseudohypoparathyroidism type 1b based on the presence of chronic HypoCa (serum Ca 1.6-1.85 mmol/l) since birth associated with significantly elevated plasma PTH levels in the range of 310-564 pg/dl (normal range 10-65) and absence of signs of Albright hereditary osteodystrophy. Laboratory workup of the proband recently showed: PTH 514 ng/L (NR 15-65) , calcium 1.81 mmol/l (NR 2.1-2.6), phosphate 1.67mmol/L (NR 0.8-1.4), magnesium 0.73 mmol/L (NR 0.7-1.0), albumin 38 g/L (NR 40-50), Alkaline phosphatase 56 U/L, eGFR &amp;gt;60 ml/min/1.73 m2, creatinine 78 umol/L and 25-hydroxyvitamin D 77 nmol/l (NR 50-120). Daily excretion of calcium was normal at 3.38 mmol and an ultrasound of the kidneys suggest nephrocalcinosis. Skeletal X-rays and bone mass densitometry were normal. Molecular studies: WES showed no potentially pathogenic variants in GNAS, PTHR, CASR, VDR, and CYP27B1 but a previously reported homozygous variant in the PTH, exon 3 (NM_000315.4: c.128G&amp;gt;A, p.Gly43Glu). This was confirmed by Sanger sequencing in the patient and two of her brothers. This variant was assessed to be likely pathogenic or likely damaging by several in silico analysis tools including Polyphen2, MutPred, PROVEAN, DEOGEN2 and VUS by ACMG, SIFT, Mutation Assessor and FATHMM. Management: Because the patient’s HypoCa was not controlled on large doses of calcitriol and calcium carbonate, a trial of teriparatide 20 mcg SC daily resulted in normalization of calcium and PTH levels. The patient reported significant improvement in her general wellbeing with loss of numbness, tingling, muscle spasms and tetany of the fingers. She has been on teriparatide for the last year with excellent improvement in her quality-of-life Conclusion: High PTH in the presence of congenital hypoCa is not always due to receptor or post-receptor defect and can be due to a mutated biologically inactive PTH. In such cases, treatment with Teriparatide may result in stabilization of biochemical profile and improve quality of life. Presentation: 6/2/2024

Biallelic variants in ERLIN1: a series of 13 individuals with spastic paraparesis.

Biallelic variants in the ERLIN1 gene were recently reported as the cause of two motor neuron degeneration diseases, SPG62 and a recessive form of amyotrophic lateral sclerosis. However, only 12 individuals from five pedigrees have been identified so far. Thus, the description of the disease remains limited. Following the discovery of a homozygous pathogenic variant in a girl with SPG62, presenting with intellectual disability, and epilepsy, we gathered the largest series of SPG62 cases reported so far (13 individuals) to better understand the phenotype associated with ERLIN1. We collected molecular and clinical data for 13 individuals from six families with ERLIN1 biallelic variants. We performed RNA-seq analyses to characterize intronic variants and used Alphafold and a transcripts database to characterize the molecular consequences of the variants. We identified three new variants suspected to alter the bell-shaped ring formed by the ERLIN1/ERLIN2 complex. Affected individuals had childhood-onset paraparesis with slow progression. Six individuals presented with gait ataxia and three had superficial sensory loss. Aside from our proband, none had intellectual disability or epilepsy. Biallelic pathogenic ERLIN1 variants induce a rare, predominantly pure, spastic paraparesis, with possible cerebellar and peripheral nerve involvement.

Prevalence and Mutation Analysis of Short-Chain acyl-CoA Dehydrogenase Deficiency Detected by Newborn Screening in Hefei, China.

Short-chain acyl-CoA dehydrogenase deficiency (SCADD) is an autosomal recessive inborn error of mitochondrial fatty acid oxidation with highly variable biochemical and genetic characteristics. The present study aimed to estimate the prevalence and genetic characteristics of SCADD in newborns identified through screening. A total of 782,930 newborns were screened for SCADD in Hefei Neonatal Screening Center from January 2016 to December 2023. The blood samples from newborns were measured by tandem mass spectrometry (MS/MS). The suspected SCADD neonates were rechecked using next-generation gene sequencing for diagnosis. Sanger sequencing was used to verify the mutation site for patients with SCADD and their parents. A total of 21 SCADD cases were confirmed, with an incidence rate of 1/37,282. Genetic mutations were identified in all 21 cases, including 15 cases of compound heterozygous variation and 6 cases of homozygous variation. Twenty-one different mutation types and forty-two mutation sites were discovered, with the most frequent mutation being c.1031A>G, accounting for 21.43% (9/42), followed by c.1130C>T, accounting for 16.67% (7/42). Our findings expand the SCADD mutational spectra. c. 1031A>G and c.1130C>T are the common mutation sites for SCADD genes in newborns. SCADD diagnosed through NBS is primarily a benign condition, and early diagnosis is not necessarily essential.

Identification of a homozygous variant in ABCG5 by panel sequencing in a Pakistani family with sitosterolemia: Genotype-phenotype correlation and management considerations

Sitosterolemia is a rare autosomal recessive disorder characterized by impaired excretion of plant sterols, leading to their accumulation in tissues and organs. We identified a hitherto unreported homozygous variant, in ATP-binding cassette sub-family G member 5 (ABCG5) (NM_022436.3) c.274A>G p.(Lys92Glu), segregating in two affected sibs (Sit1C and Sit1F) of a consanguineous Pakistani family, during genetic workup for hereditary hemolytic anemia. Both patients had anemia, history of gum bleed and easy bruising. Peripheral film revealed stomatocytes and macrothrombocytopenia. Plasma sitosterol level was found to be significantly high (27.7 mg/dL and 25.1 mg/dL for Sit1C and F respectively), confirming diagnosis of sitosterolemia in both patients. Treatment with Ezetimibe, a sterol absorption inhibitor, resulted in significant decrease in sitosterol as well as LDL-cholesterol, in these patients. This study confirms the potential of panel sequencing as a diagnostic tool for sitosterolemia. Definitive diagnosis has significant clinical implications for genetic counseling and management strategies, such as dietary modifications and successful management with Ezetimibe.

LSM7 variants involving key amino acids for LSM complex function cause a neurodevelopmental disorder with leukodystrophy and cerebellar atrophy

Cerebellar atrophy and hypoplasia are usually identified on MRI performed on children presenting signs of cerebellar ataxias, developmental delay and intellectual disability. These signs can be associated with hypo- or de-myelinating leukodystrophies. A recent study reported two cases: one child diagnosed with leukodystrophy and cerebellar atrophy, harboring a homozygous variant in LSM7 and another one who died in utero, presumed to have another homozygous variant in LSM7, based on parents' genotype. LSM7 encodes a subunit of the LSM complex, involved in pre-RNA maturation and mRNA degradation. Consequently, it has been suggested as a strong candidate disease gene. This hypothesis was supported by functional investigations of the variants. Presently, we report a patient with neurodevelopmental defects, leukodystrophy and cerebellar atrophy, harboring compound heterozygous missense variants in the LSM7 gene. One of these variants is the same as the one carried by the first case previously reported. The other one is at the same position as the variant potentially carried by the second case previously reported. Based on comparable neuroimaging, clinical features and the involvement of the same amino-acids previously demonstrated as key for LSM complex function, we confirm that LSM7 disruption causes a neurodevelopmental disorder characterized by leukodystrophy and cerebellar atrophy.

84P A rare homozygous CAPN3 variant with distinct clinical features in unrelated families of Iraqi Jewish descent

84P A rare homozygous CAPN3 variant with distinct clinical features in unrelated families of Iraqi Jewish descent

Epileptic encephalopathy linked to a DALRD3 missense variant that impairs tRNA modification

Epileptic encephalopathies are severe epilepsy syndromes characterized by early onset and progressive cerebral dysfunction. A nonsense variant in the DALR Anticodon Binding Domain Containing 3 (DALRD3) gene has been implicated in epileptic encephalopathy but no other disease-associated variants in DALRD3 have been described. In human cells, the DALRD3 protein forms a complex with the METTL2 methyltransferase to generate the 3-methylcytosine (m3C) modification in specific arginine tRNAs. Here, we identify an individual with a homozygous missense variant in DALRD3 who displays developmental delay, cognitive deficiencies, and multifocal epilepsy. The missense variant substitutes an arginine residue to cysteine (R517C) within the DALR domain of the DALRD3 protein that is required for binding tRNAs. Cells derived from the individual homozygous for the DALRD3-R517C variant exhibit reduced levels of m3C modification in arginine tRNAs, indicating that the R517C variant impairs DALRD3 function. Notably, the DALRD3-R517C protein displays reduced association with METTL2 and loss of interaction with substrate tRNAs. Our results uncover another loss-of-function variant in DALRD3 linked to epileptic encephalopathy disorders. Importantly, these findings underscore DALRD3-dependent tRNA modification as a key contributor to proper brain development and function.

535P Cytochrome c oxidase (COX) deficiency due to a novel homozygous COX6B1 pathogenic missense variant

535P Cytochrome c oxidase (COX) deficiency due to a novel homozygous COX6B1 pathogenic missense variant

74P Update on GNE-myopathy: introduction of tissue and blood biomarkers and a novel homozygous missense variant associated with early disease onset and proximal involvement

74P Update on GNE-myopathy: introduction of tissue and blood biomarkers and a novel homozygous missense variant associated with early disease onset and proximal involvement

Identification and functional analysis of novel homozygous LMF1 variants in severe hypertriglyceridemia

Identification and functional analysis of novel homozygous LMF1 variants in severe hypertriglyceridemia

Acromesomelic Dysplasia With Homozygosity for a Likely Pathogenic BMPR1B Variant: Postaxial Polydactyly as a Novel Clinical Finding.

Acromesomelic chondrodysplasias are a rare subgroup of the clinically and genetically heterogeneous osteochondrodysplasias that are characterised by abnormalities in the limb development and short stature. Here, we report a 2-year-old boy, offspring of consanguineous parents, with acromesomelic dysplasia and postaxial polydactyly in which exome sequencing identified a novel homozygous missense variant in BMPR1B. The patient showed skeletal malformation of both hands and feet that included complex brachydactyly with the thumbs most severely affected, postaxial polydactyly of both hands, shortened toes as well as a bilateral hypoplasia of the fibula. Whole trio exome sequencing was conducted to identify potential genetic variants in the patient. The analysis identified the biallelic variant NM_001203.3:c.821A > G;p.(Gln274Arg) in BMPR1B, a gene encoding bone morphogenetic protein receptor 1B. The skeletal phenotype can be brought in line with the phenotypes of previously reported cases of BMPR1B-associated chondrodysplasias. However, the postaxial polydactyly described here is a novel clinical finding in a BMPR1B-related case; notably, it has previously been reported in other acromesomelic dysplasia cases caused by homozygous pathogenic variants in GDF5-a gene which encodes for growth differentiation factor 5, a high-affinity ligand to BMPR1B.

Metabolic Adaptations in Phosphine-Resistant Tribolium castaneum Driven by Mitochondrial Enzyme Variability and Gene Expression.

Phosphine fumigation is essential for controlling storage pests like Tribolium castaneum, but its frequent application has resulted in resistance, primarily due to mutations in the Dihydrolipoamide dehydrogenase (DLD) gene associated with the rph2 allele. This study demonstrates that the Patiala population exhibits homozygous resistance variations across populations, contrasting with the susceptibility observed in laboratory cultures. Our assessment of mitochondrial DLD and Cytochrome c oxidase (COX) activities showed significantly elevated levels in the Patiala population, with increases of approximately sevenfold for DLD and 6.92-fold for COX, indicating mitochondrial adaptations for enhanced energy production. Kinetic analyses of DLD in the resistant Patiala population showed a higher Vmax (0.005 mmol/min) and a significantly increased Km (16.66 mM), indicating variations in maximal enzyme activity and substrate affinity. Furthermore, resistant T. castaneum populations displayed substantial upregulation of DLD and COX gene expression, with DLD expression increasing by 10.53-fold and COX expression peaking at 102.57-fold in Patiala. Pearson correlation analysis indicated strong positive correlations (r > 0.8) between enzymatic activity and gene expression for both DLD and COX, suggesting a coordinated role in resistance mechanisms. The PCA biplot illustrated distribution patterns of enzymatic activity and gene expression among field-resistant populations, highlighting the association between increased resistance and elevated enzymatic activity and gene expression levels. Therefore, the upregulation of DLD and COX activities in resistant populations underscores their critical roles in counteracting phosphine, reflecting metabolic reprogramming for improved energy production under stress.