Identification of a Novel RAG1 Hypomorphic Mutation in a Child Presenting with Disseminated Vaccine-Strain Varicella.

Background: Recombination-activating gene 1 (RAG1) and recombination-activating gene 2 (RAG2) encode unique lymphocyte endonuclease proteins that are crucial in T and B cell development through V(D)J recombination. RAG1 gene defects lead to variable phenotypes, ranging from immunocompetent to severe combined immunodeficiency (SCID). Curative therapy for severe manifestations can be achieved through hematopoietic stem cell transplantation (HSCT). Advances in genomic sequencing have led to the discovery of new variants and it is recognized that the level of recombinase activity correlates with disease severity. Aim: To report the clinical presentation, immunological work-up, decision process to undergo HSCT, and confirmatory genetic diagnosis in a patient who was well until her initial presentation with disseminated vaccine-strain varicella. Methods: Clinical data was gathered through retrospective chart review. Immunological investigations, targeted gene sequencing, and thymic biopsy results were reviewed. Further genetic analysis, including whole exome and whole genome sequencing was performed. Results: Whole exome sequencing identified a single missense mutation in RAG1, R474C (c.1420C>T), which would not account for the clinical presentation. Healthy individuals with only one mutation have been reported. Subsequently, whole genome sequencing revealed a novel second heterozygous missense variant, H945D (c.2833 G>T) in the RAG1 gene. Conclusion: Hypomorphic RAG1 mutations with residual activity have a diverse phenotypic expression. Identifying and understanding the implications of these mutations is crucial for disease prognostication and tailoring management. Statement of Novelty: We present a novel RAG1 missense variant, with likely complete or partial loss of function, in a patient with significant impairment in cellular immunity.

The hypoxic expression of the glucose transporter RAG1 reveals the role of the bHLH transcription factor Sck1 as a novel hypoxic modulator in Kluyveromyces lactis

ABSTRACTGlucose is the preferred nutrient for most living cells and is also a signaling molecule that modulates several cellular processes. Glucose regulates the expression of glucose permease genes in yeasts through signaling pathways dependent on plasma membrane glucose sensors. In the yeast Kluyveromyces lactis, sufficient levels of glucose induction of the low-affinity glucose transporter RAG1 gene also depends on a functional glycolysis, suggesting additional intracellular signaling. We have found that the expression of RAG1 gene is also induced by hypoxia in the presence of glucose, indicating that glucose and oxygen signaling pathways are interconnected. In this study we investigated the molecular mechanisms underlying this crosstalk. By analyzing RAG1 expression in various K. lactis mutants, we found that the bHLH transcriptional activator Sck1 is required for the hypoxic induction of RAG1 gene. The RAG1 promoter region essential for its hypoxic induction was identified by promoter deletion experiments. Taken together, these results show that the RAG1 glucose permease gene is synergistically induced by hypoxia and glucose and highlighted a novel role for the transcriptional activator Sck1 as a key mediator in this mechanism.

A molecular phylogeny of Schizothoracinae (Teleostei: Cypriniformes: Cyprinidae) based on 12 protein-coding mitochondrial genes and RAG1 gene analysis

The ever-increasing interest in the investigation of origin and speciation of schizothoracine fishes can be dated to 20th century. However, molecular phylogeny of Schizothoracinae and their phylogenetic relationships, as well as the divergence times still remain controversial. In this study, two DNA sets consisting of 12 protein-coding mitochondrial genes from 254 individuals and RAG1 gene from 106 individuals were used to reconstruct the phylogenetic relationships and calculate the divergence times among the subfamily schizothoracinae. Our results indicated that both of the data sets supported a non-monophyletic relationship due to involving of species of Barbinae. However, the phylogenetic relationships based on mtDNA genes were more reliable than that inferred from RAG1 gene. The highly specialized grade formed a monophyletic group, together with Ptychobarbus as a sister group of Diptychus and Gymnodiptychus, which was belonging to specialized grade, indicating that Ptychobarbus may be transition species to involve to highly specialized schizothoracianae. In addition, the primitive grade clustered with Percocypris pingi, a species of Barbinae. Based on mtDNA gene, the speciation time of Schizothoracinae was 66 Ma, and the divergence time of the primitive grade and Percocypris pingi was 64 Ma. The speciation times of the three grades Schizothoracinae were 57 Ma, 51 Ma and 43 Ma, respectively; and the divergence time of specialized and highly specialized grade was 46 Ma. The divergence times of three grades were not consistent with the three stages of uplift of Qinghai-Tibet Plateau, which is older than the times.

A Homozygous RAG1 Gene Mutation in a Case of Combined Immunodeficiency: Clinical, Molecular, and Computational Analysis

<b><i>Background:</i></b> The recombination-activating gene 1 and 2 (RAG1/RAG2) proteins are essential to initiate the V(D)J recombination process, the result is a diverse repertoire of antigen receptor genes and the establishment of the adaptive immunity. RAG1 mutations can lead to multiple forms of combined immunodeficiency. <b><i>Methods:</i></b> In this report, whole exome sequencing was performed in a Moroccan child suffering from combined immunodeficiency, with T and B lymphopenia, autoimmune hemolytic anemia, and cytomegalovirus (CMV) infection. <b><i>Results:</i></b> After filtering data and Sanger sequencing validation, one homozygous mutation c.2446G&#x3e;A (p.Gly816Arg) was identified in the RAG1 gene. <b><i>Conclusion:</i></b> This finding expands the spectrum of immunological and genetic profiles linked to RAG1 mutation, it also illustrates the necessity to consider RAG1 immunodeficiency in the presence of autoimmune hemolytic anemia and CMV infection, even assuming the immunological phenotype appears more or less normal.