Exome sequencing reveals novel rare variants in Iranian familial multiple sclerosis: The importance of POLD2 in the disease pathogenesis

Consanguineous marriage among familial multiple sclerosis subjects: A national registry-based study

Background

The rising prevalence of familial multiple sclerosis (MS) in Iran has spurred interest in the potential impact of parental consanguinity on the risk of developing the disease. This study aims to aggregate current knowledge on parental consanguinity and its possible effect on MS risk, particularly among familial MS patients from various regions and ethnicities in Iran. The objective is to enhance the understanding of MS genetics and encourage further research in this field.

Materials and methods

A cross-sectional study was conducted on clinically definite familial MS (FMS) patients registered in the nationwide MS registry of Iran (NMSRI). Data were extracted and supplemented with structured telephone follow-ups to gather detailed histories of MS in relatives and the familial relationships of the patients' parents. A family penetration score was proposed. Descriptive statistics and inferential statistical tests were used to analyze the data at a significance level of 0.05, adhering to ethical guidelines.

Results

Out of 19,911 individuals registered in the NMSRI, 2307 FMS patients across 13 provinces were included in the final analysis. Among these, 385 (19.3 %) reported parental consanguinity, with 283 (14.2 %) having parents who were cousins and 102 (5.1 %) having parents who were distant relatives. The data showed no significant association between parental kinship and variables such as MS phenotype, number of affected relatives with MS, hospitalization rates, and expanded disability status scale score. Similarly, MS severity did not differ based on parental consanguinity (P-value >0.05). While the rate of consanguineous marriage was higher among patients with an onset age less than 18 years, there was no statistically significant difference in disease onset age based on parental consanguinity status.

Conclusion

Our study highlights the complexity of factors influencing MS development, including genetic and environmental components. These results highlight the need for further research to achieve a more comprehensive understanding of MS etiology.

A Whole-Genome Sequencing Study Implicates GRAMD1B in Multiple Sclerosis Susceptibility

While the role of common genetic variants in multiple sclerosis (MS) has been elucidated in large genome-wide association studies, the contribution of rare variants to the disease remains unclear. Herein, a whole-genome sequencing study in four affected and four healthy relatives of a consanguineous Italian family identified a novel missense c.1801T > C (p.S601P) variant in the GRAMD1B gene that is shared within MS cases and resides under a linkage peak (LOD: 2.194). Sequencing GRAMD1B in 91 familial MS cases revealed two additional rare missense and two splice-site variants, two of which (rs755488531 and rs769527838) were not found in 1000 Italian healthy controls. Functional studies demonstrated that GRAMD1B, a gene with unknown function in the central nervous system (CNS), is expressed by several cell types, including astrocytes, microglia and neurons as well as by peripheral monocytes and macrophages. Notably, GRAMD1B was downregulated in vessel-associated astrocytes of active MS lesions in autopsied brains and by inflammatory stimuli in peripheral monocytes, suggesting a possible role in the modulation of inflammatory response and disease pathophysiology.

Investigating the role of common and rare variants in multiplex multiple sclerosis families reveals an increased burden of common risk variation

Many multiple sclerosis (MS)-associated common risk variants as well as candidate low-frequency and rare variants have been identified; however, approximately half of MS heritability remains unexplained. We studied seven multiplex MS families, six of which with parental consanguinity, to identify genetic factors that increase MS risk. Candidate genomic regions were identified through linkage analysis and homozygosity mapping, and fully penetrant, rare, and low-frequency variants were detected by exome sequencing. Weighted sum score and polygenic risk score (PRS) analyses were conducted in MS families (24 affected, 17 unaffected), 23 sporadic MS cases, 63 individuals in 19 non-MS control families, and 1272 independent, ancestry-matched controls. We found that familial MS cases had a significantly higher common risk variation burden compared with population controls and control families. Sporadic MS cases tended to have a higher PRS compared with familial MS cases, suggesting the presence of a higher rare risk variation burden in the families. In line with this, score distributions among affected and unaffected family members within individual families showed that known susceptibility alleles can explain disease development in some high-risk multiplex families, while in others, additional genetic contributors increase MS risk.

POLD2 is activated by E2F1 to promote triple-negative breast cancer proliferation

Triple-negative breast cancer (TNBC) is a highly malignant breast cancer subtype with a poor prognosis. Improved insight into the molecular biology basis of TNBC progression is urgently needed. Herein, we reported that POLD2 was highly expressed in TNBC and patients with high POLD2 expression in their tumors had poor clinical outcomes. In functional studies, knockdown of POLD2 inhibited the proliferation of TNBC. Mechanistically, we revealed that transcription factor E2F1 directly bound to the promoter of POLD2 and regulated its expression in TNBC cells, which in turn contributed to the proliferation of TNBC. Additionally, rescue experiments validated that E2F1-mediated cell proliferation in TNBC was dependent on POLD2. Taken together, our results elucidated a novel mechanism of the E2F1-POLD2 axis in TNBC proliferation, and POLD2 may be a potential therapeutic target for TNBC treatment.