Prevalence of the polymorphic H-ficolin (FCN3) genes and mannosebinding lectin-associated serine protease-2 (MASP2) in indigenous populations from the Russian Arctic regions

Lectins, being the main proteins of the lectin pathway activating the complement system, are encoded by polymorphic genes, wherein point mutations cause the protein conformation and expression to change, which turns out to have an effect on the functionality and ability to respond to the pathogen. In the current study, largescale data on the population genotype distribution of the genes for H-ficolin FCN3 rs28357092 and mannose-binding lectin-associated serine protease MASP2 rs72550870 among the indigenous peoples of the Russian Arctic regions (Nenets, Dolgans and Nganasans, a mixed population and Russians: a total sample was about 1000 newborns) have been obtained for the first time. Genotyping was carried out using RT-PCR. The frequency of the homozygous variant del/del FCN3 rs28357092 associated with the total absence of the most powerful activator of the lectin complement pathway, N-ficolin, was revealed; 0 % in the Nenets, 0.8 % in the Dolgans and Nganasans, and 3.5 % among the Russians ( p < 0.01). Analysis of the prevalence of the MASP2 genotypes has shown the predominance of the homozygous variant AA in all studied populations, which agrees with the available world data. The heterozygous genotype AG rs72550870 associated with a reduced level of protease was found to occur rarely in the Nenets, Dolgans and Nganasans compared to newborns of Caucasoid origin from Krasnoyarsk: 0.5 % versus 3.3 %, respectively. Moreover, among 323 examined Nenets, one AG carrier was identified, whereas in Russians, 16 out of 242 examined newborns were found to be AG carriers ( p < 0.001). A homozygous variant (GG) in total absence of protease with impaired binding of both MBL and ficolins was not detected in any of the 980 examined newborns. An additional analysis of infectious morbidity in Arctic populations allows one to find phenotypic characteristics related to a high functional activity of the lectin pathway of complement activation as an most important factor for the first-line of anti-infectious defense, including such new viral diseases as COVID-19.

Whole exome sequencing identifies a novel mutation in ASPM and ultra-rare mutation in CDK5RAP2 causing Primary microcephaly in consanguineous Pakistani families

Background & Objectives: Primary Microcephaly (MCPH) is a rare neurogenetic disease, manifesting congenitally reduced head circumference and non-progressive intellectual disability (ID). To date, twenty-eight genes with biallelic mutations have been reported for this disorder. The study aimed for molecular genetic characterization of Pakistani families segregating MCPH. Methods: We studied two unrelated consanguineous families (family A and B) presenting >2 patients with diagnostic symptoms of MCPH, born to asymptomatic parents. We employed whole-exome sequencing (WES) of probands to find putative causal mutations. The candidate variants were further confirmed and analyzed for co-segregation by Sanger sequencing of all available members of each family. This study was conducted at Government College University, Faisalabad, Pakistan, and Cologne Center for Genomics (CCG), University of Cologne, Germany; during 2017-2020. Results: We identified a novel homozygous variant c.10097_10098delGA, p.(Gly3366Glufs*19) in exon 26 of ASPM gene in family A which presents with moderate intellectual disability, speech impairment, visual abnormalities, seizures, and ptyalism. Family B was found to segregate nonsense, homozygous variant c.448C>T p.(Arg150*) in CDK5RAP2. The patients also exhibited mild to severe seizures without ptyalism that has not been previously reported in patients with mutations in the CDK5RAP2 gene. Conclusion: We report a novel mutation in ASPM and ultra-rare mutation in the CDK5RAP2 gene, both causing primary microcephaly. The study expands the mutational spectrum of the ASPM gene to 212, and also adds to the clinical spectrum of CDK5RAP2 mutations. It also demonstrated the utility of WES in the investigation and genetic diagnosis of genetically heterogeneous disorders like MCPH. These findings would aid in diagnostic and preventive strategies including carrier screening, cascade testing, and genetic counselling. doi: https://doi.org/10.12669/pjms.38.1.4464 How to cite this:Makhdoom EH, Anwar H, Baig SM, Hussain G. Whole exome sequencing identifies a novel mutation in ASPM and ultra-rare mutation in CDK5RAP2 causing Primary microcephaly in consanguineous Pakistani families. Pak J Med Sci. 2022;38(1):---------. doi: https://doi.org/10.12669/pjms.38.1.4464 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Heterozygous NUDT15 Gene Polymorphism Would Not Associate with the Severity of 6-Mercaptopurine Side Effects in Early Intensification Therapy for Childhood Acute Lymphoblastic Leukemia

Background In the treatment of childhood acute lymphoblastic leukemia (ALL), 6-mercaptopurine (6-MP) is essential for early intensification and maintenance therapy. Recently, it has been reported that a gene polymorphism of nucleoside diphosphate-linked moiety X-type motif 15 (NUDT15) rs116855232 is associated with the 6-MP induced severe myelotoxicity. Since the NUDT15 rs116855232 polymorphism is relatively common in East Asian and Hispanic populations, it is important to evaluate the association between the polymorphism and 6-MP for determining the dose of effective therapy and avoiding the side effect in Japan. However, there are few reports on the association between NUDT15 polymorphisms and the therapeutic efficacy or side effects of 6-MP in the early intensification; most previous reports focused on the maintenance therapy so far. The purpose of this study is to clarify the association between NUDT15 polymorphism and the actual treatment status with 6-MP or its side effects, therefore to contribute to the effective and safe treatment of childhood ALL in Japan. Methods Twenty-four patients with ALL who received early intensification therapy according to the JPLSG ALL-B12 or JPLSG ALL-T11 protocol at the Department of Pediatrics, Hokkaido University Hospital, between April 2013 and May 2021 were included in the study. We retrospectively collected the clinical and laboratory data from the clinical records. And we also performed the sequence analysis of the exon 1 and 3 in NUDT15 gene Results Genetic analysis of NUDT15 showed no nucleotide changes other than rs116855232. Twenty patients were CC (wild-type), 4 patients were CT (heterozygous-variant), and 0 patients were TT (homozygous-variant). Of the 4 patients with heterozygous-variant, one patient received a reduced dose of 6-MP because of early onset myelotoxicity during early intensification therapy. In this patient, the total dose of 6-MP was 70% of the standard dose. All the 24 patients showed myelotoxicity and hepatotoxicity during early intensification therapy. Correlations between NUDT15 haplotype and side effects as myelotoxicity and hepatotoxicity were not significant. Discussion In the heterozygous-variant of NUDT15 rs116855232, the incidence and degree of myelotoxicity and hepatotoxicity during early intensification therapy did not differ from the wild-type. The international consortium (Clinical Pharmacogenetics Implementation Consortium Guideline, 2018) recommends that the dose of 6-MP should be reduced to 10mg/m2/day in patients with homozygous variant of NUDT15, however, the reduction of the starting dose of 6-MP in those with heterozygous variant is not recommended. Of note, these recommendations were made based on the data in the maintenance therapy. Our study suggests that the reduction of the starting dose may not be necessary in children with heterozygous variant. The NUDT15 rs116855232 polymorphism is common in Japan, with 10% of heterozygotes and 1.1% of homozygotes. In future study, a larger study on the association between NUDT15 polymorphism and treatment outcome including side effects in the early intensification is needed in East Asia to confirm the results of our study. Disclosures No relevant conflicts of interest to declare.

A Novel BBS9 Mutation Identified via Whole-Exome Sequencing in a Chinese Family with Bardet-Biedl Syndrome

Bardet-Biedl syndrome (BBS) is a genetically heterogeneous disorder characterized by polydactyly, obesity, rod-cone dystrophy, and mental retardation. Twenty-one genes have been identified as causing BBS. This study collected a BBS pedigree from two patients and performed whole-exome sequencing on one patient. We identified a novel homozygous variant c.1114C>T (p.Q372X) in the BBS9 of the two siblings. This variant was confirmed and completely cosegregated with the disease of this family by Sanger sequencing. We report a novel homozygous variant c.1114C>T in the BBS9 gene in a Chinese family.

Mutated VWA8 Is Associated With Developmental Delay, Microcephaly, and Scoliosis and Plays a Novel Role in Early Development and Skeletal Morphogenesis in Zebrafish

Von Willebrand A domain-containing protein 8 (VWA8), also named KIAA0564, is a poorly characterized, mitochondrial matrix-targeted protein having a putative ATPase activity. VWA8 is comprising of ATPase-associated domains and a VWFA domain associated with ATPase activity inside the cell. In the present study, we describe a large consanguineous family of Saudi origin segregating a complex developmental syndrome in an autosomal recessive fashion. All the affected individuals exhibited severe developmental disorders. DNA from three patients was subjected to whole-exome sequencing followed by Sanger sequencing. VWA8 knock-down zebrafish morpholinos were used to study the phenotypic effect of this gene on zebrafish development. A homozygous missense variant [c.947A &gt; G; p.(Asp316Gly)] was identified in exon 8 of the VWA8 gene, which perfectly segregated with the disease phenotype. Using zebrafish morpholino, we observed delayed development at an early stage, lack of movement, light sensitivity, severe skeletal deformity such as scoliosis, and facial dysmorphism. This is the first homozygous variant identified in the VWA8 gene underlying global developmental delay, microcephaly, scoliosis, limbs, and cardiovascular malformations in humans. We provide genetic and molecular evidence using zebrafish morpholino for a homozygous variant in the VWA8 gene, associated with such a complex developmental syndrome in humans.

Ichthyosis Prematurity Syndrome: A Rare Form but Easily Recognizable Ichthyosis

Ichthyosis prematurity syndrome is a rare autosomal recessive genodermatosis that is associated with mutations in the <i>SLC27A4</i> gene. Its onset occurs in early childhood and presents with the clinical triad of premature birth, thick caseous desquamating epidermis, and neonatal asphyxia. Here, we describe a prematurely born baby patient (33 weeks of gestation) with a homozygous variant at the initiation codon site (<i>c</i>.<i>1</i> A&#x3e; <i>G</i>, <i>p</i>.<i>Met1Val</i>) in the <i>SLC27A4</i> gene to raise awareness of this rare syndrome despite its distinctive features as we believe it is still underdiagnosed.