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

Neurodevelopmental disorders associated variants in ADAT3 disrupt the activity of the ADAT2/ADAT3 tRNA deaminase complex and impair neuronal migration

The ADAT2/ADAT3 complex catalyzes the adenosine to inosine modification at the wobble position of eukaryotic tRNAs. Mutations in ADAT3 , the catalytically inactive subunit of the ADAT2/ADAT3 complex, have been identified in patients presenting with severe neurodevelopmental disorders (NDDs). Yet, the physiological function of ADAT2/ADAT3 complex during brain development remains totally unknown. Here we showed that maintaining a proper level of ADAT2/ADAT3 catalytic activity is required for correct radial migration of projection neurons in the developing mouse cortex. In addition, we not only reported 7 new NDD patients carrying biallelic variants in ADAT3 but also deeply characterize the impact of those variants on ADAT2/ADAT3 structure, biochemical properties, enzymatic activity and tRNAs editing and abundance. We demonstrated that all the identified variants alter both the expression and the activity of the complex leading to a significant decrease of I 34 with direct consequence on their steady-state. Using in vivo complementation assays, we correlated the severity of the migration phenotype with the degree of the loss of function caused by the variants. Altogether, our results indicate a critical role of ADAT2/ADAT3 during cortical development and provide cellular and molecular insights into the pathogenicity of ADAT3-related neurodevelopmental disorder.

Consanguinity and willingness to perform premarital genetic screening in Sudan

Consanguineous marriage is prevalent in certain world regions due to cultural, economic, and social reasons. However, it can lead to negative consequences including an increased risk of genetic disorders in offspring. Premarital genetic screening (PMGS) is an important tool to identify and manage these risks before marriage. This study aimed to assess the magnitude of consanguineous marriage, knowledge of genetic diseases and PMGS, and attitudes and willingness to perform PMGS in Sudan. A national household survey was conducted using a multistage sampling technique, with a sample size of 2272 participants. Data were collected from December 2022 to March 2023 using an interviewer-administered questionnaire. A significant proportion of respondents (364/850, 42.8%) were married to consanguineal partners, with various types of relatedness. Moreover, 32.1% (242/755) of single respondents were planning to marry a close relative, signifying the likely persistence of consanguineous marriages in Sudan. The level of knowledge regarding genetic diseases and PMGS was relatively low in many states of Sudan, indicating the need for increased awareness interventions. A significant number of participants (85.2%) agreed that premarital screening is effective in reducing genetic diseases, whereas 71.2% supported the introduction of a mandatory PMGS program. Excluding married participants, 82.3% (1265/1537) of respondents were willing to perform PMGS, if implemented. These findings reflect the public positive attitude towards introducing the PMGS program and policies in Sudan and underscore the importance of addressing the knowledge gap of PMGS before such a potential implementation.

Regulatory network and targeted interventions for CCDC family in tumor pathogenesis

CCDC (coiled-coil domain-containing) is a coiled helix domain that exists in natural proteins. There are about 180 CCDC family genes, encoding proteins that are involved in intercellular transmembrane signal transduction and genetic signal transcription, among other functions. Alterations in expression, mutation, and DNA promoter methylation of CCDC family genes have been shown to be associated with the pathogenesis of many diseases, including primary ciliary dyskinesia, infertility, and tumors. In recent studies, CCDC family genes have been found to be involved in regulation of growth, invasion, metastasis, chemosensitivity, and other biological behaviors of malignant tumor cells in various cancer types, including nasopharyngeal carcinoma, lung cancer, colorectal cancer, and thyroid cancer. In this review, we summarize the involvement of CCDC family genes in tumor pathogenesis and the relevant upstream and downstream molecular mechanisms. In addition, we summarize the potential of CCDC family genes as tumor therapy targets. The findings discussed here help us to further understand the role and the therapeutic applications of CCDC family genes in tumors.

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.