Insulators are regulatory elements that help to organize eukaryotic chromatin via enhancer-blocking and chromatin barrier activity. Although there are several examples of transposable element ...(TE)-derived insulators, the contribution of TEs to human insulators has not been systematically explored. Mammalian-wide interspersed repeats (MIRs) are a conserved family of TEs that have substantial regulatory capacity and share sequence characteristics with tRNA-related insulators. We sought to evaluate whether MIRs can serve as insulators in the human genome. We applied a bioinformatic screen using genome sequence and functional genomic data from CD4⁺ T cells to identify a set of 1,178 predicted MIR insulators genome-wide. These predicted MIR insulators were computationally tested to serve as chromatin barriers and regulators of gene expression in CD4⁺ T cells. The activity of predicted MIR insulators was experimentally validated using in vitro and in vivo enhancer-blocking assays. MIR insulators are enriched around genes of the T-cell receptor pathway and reside at T-cell–specific boundaries of repressive and active chromatin. A total of 58% of the MIR insulators predicted here show evidence of T-cell–specific chromatin barrier and gene regulatory activity. MIR insulators appear to be CCCTC-binding factor (CTCF) independent and show a distinct local chromatin environment with marked peaks for RNA Pol III and a number of histone modifications, suggesting that MIR insulators recruit transcriptional complexes and chromatin modifying enzymes in situ to help establish chromatin and regulatory domains in the human genome. The provisioning of insulators by MIRs across the human genome suggests a specific mechanism by which TE sequences can be used to modulate gene regulatory networks.
The temporal and spatial regulation of gene expression in mammalian development is linked to the establishment of functional chromatin domains. Here, we report that tissue-specific transcription of a ...retrotransposon repeat in the murine growth hormone locus is required for gene activation. This repeat serves as a boundary to block the influence of repressive chromatin modifications. The repeat element is able to generate short, overlapping Pol II-and Pol III-driven transcripts, both of which are necessary and sufficient to enable a restructuring of the regulated locus into nuclear compartments. These data suggest that transcription of interspersed repetitive sequences may represent a developmental strategy for the establishment of functionally distinct domains within the mammalian genome to control gene activation.
Summary
Albinism is a rare genetic condition globally characterized by a number of specific deficits in the visual system, resulting in poor vision, in association with a variable hypopigmentation ...phenotype. This lack or reduction in pigment might affect the eyes, skin, and hair (oculocutaneous albinism, OCA), or only the eyes (ocular albinism, OA). In addition, there are several syndromic forms of albinism (e.g. Hermansky–Pudlak and Chediak–Higashi syndromes, HPS and CHS, respectively) in which the described hypopigmented and visual phenotypes coexist with more severe pathological alterations. Recently, a locus has been mapped to the 4q24 human chromosomal region and thus represents an additional genetic cause of OCA, termed OCA5, while the gene is eventually identified. In addition, two new genes have been identified as causing OCA when mutated: SLC24A5 and C10orf11, and hence designated as OCA6 and OCA7, respectively. This consensus review, involving all laboratories that have reported these new genes, aims to update and agree upon the current gene nomenclature and types of albinism, while providing additional insights from the function of these new genes in pigment cells.
Inherited hearing impairment is a remarkably heterogeneous monogenic condition, involving hundreds of genes, most of them with very small (< 1%) epidemiological contributions. The exception is GJB2, ...the gene encoding connexin-26 and underlying DFNB1, which is the most frequent type of autosomal recessive non-syndromic hearing impairment (ARNSHI) in most populations (up to 40% of ARNSHI cases). DFNB1 is caused by different types of pathogenic variants in GJB2, but also by large deletions that keep the gene intact but remove an upstream regulatory element that is essential for its expression. Such large deletions, found in most populations, behave as complete loss-of-function variants, usually associated with a profound hearing impairment. By using CRISPR-Cas9 genetic edition, we have generated a murine model (Dfnb1
) that reproduces the most frequent of those deletions, del(GJB6-D13S1830). Dfnb1
homozygous mice are viable, bypassing the embryonic lethality of the Gjb2 knockout, and present a phenotype of profound hearing loss (> 90 dB SPL) that correlates with specific structural abnormalities in the cochlea. We show that Gjb2 expression is nearly abolished and its protein product, Cx26, is nearly absent all throughout the cochlea, unlike previous conditional knockouts in which Gjb2 ablation was not obtained in all cell types. The Dfnb1
model recapitulates the clinical presentation of patients harbouring the del(GJB6-D13S1830) variant and thus it is a valuable tool to study the pathological mechanisms of DFNB1 and to assay therapies for this most frequent type of human ARNSHI.
Albinism in Europe Mártinez-García, Mónica; Montoliu, Lluís
Journal of dermatology,
05/2013, Letnik:
40, Številka:
5
Journal Article
Recenzirano
Albinism is a rare genetic condition associated with a variable hypopigmentation phenotype, which can affect the pigmentation of only the eyes or both the eyes and the skin/hair, resulting in ocular ...(OA) or oculocutaneous albinism (OCA), respectively. At least four forms of OCA and one of OA are known, associated with TYR (OCA1), OCA2 (OCA2), TYRP1 (OCA3), SLC45A2 (OCA4) and GPR143 (OA1) loci, respectively. Additionally, the rarest syndromic forms of albinism, affecting the normal function of other organs, can be grouped in Hermansky–Pudlak syndrome (HPS1–9) and the Chediak–Higashi syndrome (CHS1). In summary, a total of 15 genes are currently associated with various types of albinism. However, new genes have been recently described, associated with autosomal recessive oculocutaneous albinism with highly similar phenotypes but diverse molecular origin, indicating that there are likely to be more than 15 genes whose mutations will be associated with albinism. In this review, we will describe the different types of albinism and comment on its prevalence in European countries. Some preclinical attempts for innovative therapeutic approaches of different types of albinism will be also discussed.
Conditional mutagenesis using Cre recombinase expressed from tissue specific promoters facilitates analyses of gene function and cell lineage tracing. Here, we describe two novel dual-promoter-driven ...conditional mutagenesis systems designed for greater accuracy and optimal efficiency of recombination. Co-Driver employs a recombinase cascade of Dre and Dre-respondent Cre, which processes loxP-flanked alleles only when both recombinases are expressed in a predetermined temporal sequence. This unique property makes Co-Driver ideal for sequential lineage tracing studies aimed at unraveling the relationships between cellular precursors and mature cell types. Co-InCre was designed for highly efficient intersectional conditional transgenesis. It relies on highly active trans-splicing inteins and promoters with simultaneous transcriptional activity to reconstitute Cre recombinase from two inactive precursor fragments. By generating native Cre, Co-InCre attains recombination rates that exceed all other binary SSR systems evaluated in this study. Both Co-Driver and Co-InCre significantly extend the utility of existing Cre-responsive alleles.
PurposeWe aimed to generate and phenotype a mouse model of foveal hypoplasia, optic nerve decussation defects, and anterior segment dysgenesis (FHONDA), a rare disease associated with mutations in ...Slc38a8 that causes severe visual alterations similar to albinism without affecting pigmentation.MethodsThe FHONDA mouse model was generated with clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology using an RNA guide targeting the Scl38a8 murine locus. The resulting mice were backcrossed to C57BL/6J. Melanin content was measured using spectrophotometry. Retinal cell architecture was analyzed through light and electron microscopy. Retinal projections to the brain were evaluated with anterograde labelling in embryos and adults. Visual function was assessed by electroretinography (ERG) and the optomotor test (OT).ResultsFrom numerous Slc38a8 mouse mutant alleles generated, we selected one that encodes a truncated protein (p.196Pro*, equivalent to p.199Pro* in the human protein) closely resembling a mutant allele described in patients (p.200Gln*). Slc38a8 mutant mice exhibit wild-type eye and coat pigmentation with comparable melanin content. Subcellular abnormalities were observed in retinal pigment epithelium cells of Slc38a8 mutant mice. Anterograde labeling experiments of retinal projections in embryos and adults showed a reduction of ipsilateral fibers. Functional visual analyses revealed a decreased ERG response in scotopic conditions and a reduction of visual acuity in mutant mice measured by OT.ConclusionsSlc38a8 mutant mice recapitulate the phenotype of patients with FHONDA concerning their normal pigmentation and their abnormal visual system, in the latter being a hallmark of all types of albinism. These mice will be helpful in better understanding the pathophysiology of this genetic condition.
Physical exercise is a robust lifestyle intervention. Among its many benefits, it is known for its enhancement of cognitive abilities. Nevertheless, the extent to which these benefits can be ...transmitted across generations (intergenerational inheritance to F1, and transgenerational to F2 and beyond) remains a topic of limited comprehension. We have already shown that cognitive improvements resulting from physical exercise can be inherited from parents to their offspring, proving intergenerational effects. So, we set out to explore whether these enhancements might extend transgenerationally, impacting the F2 generation. In this study, we initially examined the behavioral traits of second-generation (F2) male mice, whose grandfathers (F0) had an exercise intervention. Our findings revealed that F2 mice with physically active F0 grandparents displayed significantly improved memory recall, encompassing both spatial and non-spatial information when compared to their counterparts from sedentary F0 progenitors, and proving for the first time the transgenerational inheritance of physical exercise-induced cognitive enhancement. Surprisingly, while F2 memory improved (as in F1), adult hippocampal neurogenesis remained unchanged between experimental and control groups (unlike in F1). Additionally, our analysis of smallRNA sequences in hippocampus identified 35 differentially expressed miRNAs linked to important brain function categories. Notably, two of these miRNAs, miRNA-144 and miRNA-298, displayed robust negative correlation with cognitive performance. These findings highlight enduring transgenerational transmission of cognitive benefits associated with exercise, even after two generations. Furthermore, they suggest that moderate exercise training can have lasting positive effects, possibly orchestrated by a specific set of miRNAs that exert their influence across multiple generations.
Physical exercise is well known by its positive effects on body health and specifically on brain functioning and health. Here we test whether those effects are inherited from exercised grandparents to the second generation. We report here for the first time the transgenerational inheritance of moderate exercise-induced grandpaternal traits in grandson's cognition, even though some of the cellular changes induced in F1 vanish in F2, and suggesting that moderate exercise training has a longer-lasting effect than previously thought, most probably mediated by a small group of microRNAs acting across generations.
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