POLD3 deficiency is associated with severe combined immunodeficiency, neurodevelopmental delay, and hearing impairment

Genetic analysis of comorbidities between osteoarthritis, sarcopenia, and osteoporosis

BACKGROUND

Osteoarthritis (OA), sarcopenia (SCP), and osteoporosis (OP) pose a substantial global morbidity and mortality burden, and previous studies have observed potential associations among them. This study aims to comprehensively characterize the common genetic structure, biological basis, and underlying causal relationship among OA, SCP, and OP.

METHODS

We used pooled statistics from the largest European genome-wide association study to investigate the genetic overlap and underlying causal relationships among OA, SCP, and OP. LD Score Regression (LDSC) was first used for estimating global and local genetic associations, cross-trait meta-analysis was then conducted to identify shared loci, and mendelian randomization (MR) analysis was performed to test causal association.

RESULTS

In global and local genetic correlation analysis, we found strong positive correlations among OA, SCP, and OP. Cross-trait meta-analysis revealed 9 novel pleiotropic loci for HandOA_SCP trait-pairs, 1 for ThumbOA_SCP (females), and 6 for KneeOA_SCP (males)0.10 novel pleiotropic loci were also identified for HipOA_TBMD, while none for WLM_FinOP. Bidirectional MR analyses indicated significant causal associations between HandOA and SCP(Forward: OR: 1.41, 95 % CI: 1.25-1.60, p < 0.01,Reverse: OR: 1.77, 95 % CI: 1.34-2.35, p < 0.01). Reverse analyses suggested that ThumbOA.female (OR: 1.92, 95 % CI:1.18-3.13, p < 0.01) and KneeOA.male (OR: 1.58, 95 % CI: 1.13-2.12, p < 0.01) were positively correlated with SCP, while TBMD was positively correlated with HipOA (OR: 1.23, 95 % CI: 1.16-1.31, p < 0.01).

CONCLUSIONS

Our work demonstrates a shared genetic basis, pleiotropic loci, and putative causal relationships among OA, SCP, and OP, highlighting the intrinsic links behind these three complex skeletal diseases.

Mechanistic Insights into Drug-Induced Guillain-Barré Syndrome: A Large-Cohort Analysis of the FAERS Database

Background/Objectives: Drug-induced Guillain-Barré Syndrome (GBS) is a severe complication of pharmacotherapy. Previous research has established a connection between certain medications and higher GBS risk. However, a large-cohort analysis is crucial to reveal underlying biological mechanisms of drug-induced GBS. This study aimed to evaluate the association between GBS and various drugs currently accessible in the Food and Drug Administration Adverse Event Reporting System (FAERS) database and explore the mechanisms underlying drug-induced GBS. Methods: We analyzed drug-induced GBS adverse event reports in the FAERS database to identify strongly associated drugs. We then investigated GBS susceptibility proteins through GWAS meta-analysis and Mendelian Randomization (MR) based on plasma proteomics, complemented by protein-protein interaction (PPI) network analysis to explore underlying mechanisms. Results: A total of 4094 FAERS reports were analyzed, leading to the selection of 30 drugs with the highest signal strength and 54 drug targets. MR analysis identified 73 susceptibility proteins linked to GBS risk. PPI analysis revealed that 10 genes encoding GBS-susceptible proteins were associated with 19 drug target genes involved in 13 different drugs. Among these, the antineoplastic drug Nelarabine showed the strongest correlation with GBS. The TNF and PDCD1LG2 genes emerged as key GBS-susceptible genes. Additionally, TNF was negatively correlated with GBS, and PDCD1LG2 was positively correlated with GBS. KEGG analysis indicated that pyrimidine metabolism, purine metabolism, and the IL6/JAK/STAT3 signaling pathway also significantly contribute to drug-induced GBS. Conclusions: This study improved our understanding of the biological mechanisms of drug-induced GBS, thereby pinpointing potential therapeutic targets for future intervention.

Update on inborn errors of immunity

Ever since the first description of an inherited immunodeficiency in 1952 in a boy with gammaglobulin deficiency, new insights have progressed rapidly in disorders that are now referred to as inborn errors of immunity. In a field where fundamental molecular biology, genetics, immune signaling, and clinical care are tightly intertwined, 2022-24 saw a multitude of advances. Here we report a selection of research updates with a main focus on (1) diagnosis and screening, (2) new genetic defects, (3) susceptibility to severe coronavirus disease 2019 infection and impact of vaccination, and (4) treatment. Importantly, new pathogenic insights more rapidly affect treatment outcomes, either through an earlier and more precise diagnosis or through implementation of novel, personalized treatment. The field is growing rapidly, so awareness, communication, and collaboration are key to improving treatment outcomes.

POLD3 haploinsufficiency is linked to non-syndromic sensorineural adult-onset progressive hearing and balance impairments

Hearing impairment (HI) is a significant health concern globally, influenced by genetic and environmental factors. We had identified a homozygous pathogenic variant in POLD3 in a Lebanese patient with an autosomal congenital recessive syndromic hearing loss (MIM#620869). This variant was found at heterozygous state in the parents, who developed progressive hearing impairment around age 40. We conducted a thorough clinical and genetic assessment of sixteen family members, including physical exams, audiometry and vestibular function evaluations. Additionally, gene expression analysis of the Pold3 gene was performed in mice using RNAscope. Twelve individuals were heterozygous for the variant in POLD3, of whom eight showed bilateral adult-onset HI, typically starting around ages 40-50, and two older patients displaying unilateral vestibular weakness. Additionally, two carriers of the variant developed cancer at an early age. RNAscope confirmed Pold3 expression in auditory and vestibular neurons. Exome sequencing analysis excluded the presence of pathogenic variants in any known hearing impairment or cancer predisposition genes. We present herein, for the first time, evidence of a heterozygous pathogenic POLD3 variant associated with a novel form of autosomal dominant progressive adult-onset hearing and vestibular impairments. We also highlight the necessity for further exploration of the role of POLD3 in cancer predisposition.

POLD3 as Controller of Replicative DNA Repair

Multiple modes of DNA repair need DNA synthesis by DNA polymerase enzymes. The eukaryotic B-family DNA polymerase complexes delta (Polδ) and zeta (Polζ) help to repair DNA strand breaks when primed by homologous recombination or single-strand DNA annealing. DNA synthesis by Polδ and Polζ is mutagenic, but is needed for the survival of cells in the presence of DNA strand breaks. The POLD3 subunit of Polδ and Polζ is at the heart of DNA repair by recombination, by modulating polymerase functions and interacting with other DNA repair proteins. We provide the background to POLD3 discovery, investigate its structure, as well as function in cells. We highlight unexplored structural aspects of POLD3 and new biochemical data that will help to understand the pivotal role of POLD3 in DNA repair and mutagenesis in eukaryotes, and its impact on human health.

Case of T-B+NK+ X-Linked Severe Combined Immunodeficiency Disease

We report a case of T-B+NK+ severe combined immunodeficiency disease (SCID) caused by IL2RG gene mutation (NM_000206.3 [IL2RG]: c.925-2A > G). The patient, a 2-month-old male, experienced multiple infections and decreased white blood cells in the early postnatal period. Antibiotic treatment was ineffective and ultimately resulted in multiple organ failure. The second-generation gene sequencing of patient showed that the IL2RG gene had a hemizygous mutation NM_000206.3 (IL2RG): c.925-2A > G, indicating a classical splice site mutation. According to the guidelines of the American College of Medical Genetics (ACMG), NM_00206.3 (IL2RG): c.925-2A > G variants can be classified as pathogenic (PVS1&PM1&PM6).

Human Autosomal Recessive DNA Polymerase Delta 3 Deficiency Presenting as Omenn Syndrome

The DNA polymerase δ complex (PolD), comprising catalytic subunit POLD1 and accessory subunits POLD2, POLD3, and POLD4, is essential for DNA synthesis and is central to genome integrity. We identified, by whole exome sequencing, a homozygous missense mutation (c.1118A > C; p.K373T) in POLD3 in a patient with Omenn syndrome. The patient exhibited severely decreased numbers of naïve T cells associated with a restricted T-cell receptor repertoire and a defect in the early stages of TCR recombination. The patient received hematopoietic stem cell transplantation at age 6 months. He manifested progressive neurological regression and ultimately died at age 4 years. We performed molecular and functional analysis of the mutant POLD3 and assessed cell cycle progression as well as replication-associated DNA damage. Patient fibroblasts showed a marked defect in S-phase entry and an enhanced number of double-stranded DNA break-associated foci despite normal expression levels of PolD components. The cell cycle defect was rescued by transduction with WT POLD3. This study validates autosomal recessive POLD3 deficiency as a novel cause of profound T-cell deficiency and Omenn syndrome.