As compared to mice who had received bone marrow cells, gene therapy-treated mice showed significant improvement of T and B cell counts, although these remained lower than what observed in mice transplanted with wild-type bone marrow cells. PID, and in some cases may even represent the predominant manifestation. Recognition of such expanded phenotypic spectrum has been also facilitated by advances in molecular genetics, in particular development of targeted sequencing panels and whole exome/whole genome sequencing (WES, WGS). These approaches have permitted to appreciate that different mutations in the same gene may even underlie distinct clinical phenotypes. Furthermore, careful biochemical analysis has revealed that such phenotypic heterogeneity may also be contributed by different mechanisms of disease, including loss-of-function (LOF), haploinsufficiency, dominant unfavorable, and gain-of-function (GOF) effects. In this regard, the study of human diseases (and PID in particular) has rapidly overcome some intrinsic limitations of animal models, that for many decades have largely been based on gene disruption. Mutations of the Recombinase Activating Genes 1 and 2 (mutations underlie a continuum of degree of catalytic function mediated by the RAG complex. This translates in a variable degree of impairment of T and B cell development, affecting composition and diversity of the immune repertoire and immune homeostasis. Consequently, mutations have been associated with severe combined immunodeficiency with absence of T and B cells (T? B? SCID), Omenn syndrome (OS) with presence of oligoclonal and activated T cells infiltrating and damaging target tissues, atypical SCID (AS) with residual presence of oligoclonal T (and occasionally, B) cells, and combined immunodeficiency associated with granulomas and/or autoimmunity (CID-G/AI) (3). Overall, recognition of this Rivastigmine broad spectrum of clinical and immunological phenotypes underpins the crucial role of the RAG complex in immune homeostasis. Here, we will discuss recent advances in the mechanisms underlying the pathophysiology of the immune dysregulation associated with hypomorphic mutations in Rivastigmine patients and in animal models. Molecular and biochemical structure of human RAG1 and RAG2 The generation of an extensive repertoire of immunoglobulin and T cell receptor (TCR) molecules in developing lymphocytes is usually ensured by the combinatorial association of dispersed variable (and gene segments made up of conserved consensus nonamer and heptamer elements separated by a degenerate spacer of Rivastigmine either 12 or 23 nucleotides are recognized by the Recombination activating gene proteins, RAG1 and RAG2 (5). Expression of RAG genes is usually tightly regulated and occurs at early stages of T and B cell differentiation. The RAG Keratin 7 antibody proteins form a heterotetramer with two subunits each of RAG1 and RAG2, that recognizes and binds to a pair of RSSs, introducing a DNA double strand break at the junction with the coding gene segment. Efficient recombination occurs only when Rivastigmine the RAGs bind one 12RSS and one 23RSS (the so called 12/23 rule). However, in the rearrangement of T-cell receptor beta and delta loci, joining of and gene segments bordered by the 23 and 12 RSS does not occur, and an intervening segment has to be joined to before a segment can be joined to the rearranged product (the so-called beyond 12/23 restriction) (6, 7). The human and genes are located in a tail to tail configuration on chromosome 11p13 and are separated by only 8 kb (8). Both the genomic organization of the genes and the amino acid composition of the RAG proteins are highly conserved throughout evolution. Furthermore, the observation that RAG proteins share similarities with various transposases and can mediate transposition (9, 10), supports the hypothesis that RAG recombinase originates from a common transponsable element that joined the genome of a common ancestor of all jawed vertebrate. Consistent with this hypothesis, the transposon superfamily has been recently identified in the genome of the basal chordate amphioux (11C13). Multiple levels of regulation of gene expression have been hypothesized to occur because of the on-off fluctuation observed during lymphocyte development. Furthermore, expression of the RAG proteins is also regulated at the post-translational level. and data indicate the presence of cis-regulatory elements in the locus, and an additional regulatory mechanism has been described to mediate the regulated degradation of the RAG2 protein via phosphorylation.
As compared to mice who had received bone marrow cells, gene therapy-treated mice showed significant improvement of T and B cell counts, although these remained lower than what observed in mice transplanted with wild-type bone marrow cells