Project description:Myotonic dystrophy type 1 is a dominantly inherited multisystemic disease caused by CTG tandem repeat expansions in the DMPK 3' untranslated region. These expanded repeats are transcribed and produce toxic CUG RNAs that sequester and inhibit activities of the MBNL family of developmental RNA processing factors. Although myotonic dystrophy is classified as a muscular dystrophy, the brain is also severely affected by an unusual cohort of symptoms, including hypersomnia, executive dysfunction, as well as early onsets of tau/MAPT pathology and cerebral atrophy. To address the molecular and cellular events that lead to these pathological outcomes, we recently generated a mouse Dmpk CTG expansion knockin model and identified choroid plexus epithelial cells as particularly affected by the expression of toxic CUG expansion RNAs. To determine if toxic CUG RNAs perturb choroid plexus functions, alternative splicing analysis was performed on lateral and hindbrain choroid plexi from Dmpk CTG knockin mice. Choroid plexus transcriptome-wide changes were evaluated in Mbnl2 knockout mice, a developmental-onset model of myotonic dystrophy brain dysfunction. To determine if transcriptome changes also occurred in the human disease, we obtained post-mortem choroid plexus for RNA-seq from donors without neurologically unaffected (two females, three males; ages 50-70) and myotonic dystrophy type 1 donors (one female, three males; ages 50-70). To test that choroid plexus transcriptome alterations resulted in altered CSF composition, we obtained CSF via lumbar puncture from patients with myotonic dystrophy type 1 (five females, five males; ages 35-55) and non-myotonic dystrophy patients (three females, four males; ages 26-51) and Western blot and osmolarity analyses were used to test CSF alterations predicted by choroid plexus transcriptome analysis. We determined that CUG RNA induced toxicity was more robust in the lateral choroid plexus of Dmpk CTG knockin mice due to comparatively higher Dmpk and lower Mbnl RNA levels. Impaired transitions to adult splicing patterns during choroid plexus development were identified in Mbnl2 knockout mice, including mis-splicing previously found in Dmpk CTG knockin mice. Whole transcriptome analysis of myotonic dystrophy type 1 choroid plexus revealed disease-associated RNA expression and mis-splicing events. Based on these RNA changes, predicted alterations in ion homeostasis, secretory output, and CSF composition were confirmed by analysis of myotonic dystrophy type 1 CSF. Our results implicate choroid plexus spliceopathy and concomitant alterations in CSF homeostasis as an unappreciated contributor to myotonic dystrophy type 1 CNS pathogenesis.
Project description:Myotonic dystrophy type 1 is a dominantly inherited multisystemic disease caused by CTG tandem repeat expansions in the DMPK 3' untranslated region. These expanded repeats are transcribed and produce toxic CUG RNAs that sequester and inhibit activities of the MBNL family of developmental RNA processing factors. Although myotonic dystrophy is classified as a muscular dystrophy, the brain is also severely affected by an unusual cohort of symptoms, including hypersomnia, executive dysfunction, as well as early onsets of tau/MAPT pathology and cerebral atrophy. To address the molecular and cellular events that lead to these pathological outcomes, we recently generated a mouse Dmpk CTG expansion knockin model and identified choroid plexus epithelial cells as particularly affected by the expression of toxic CUG expansion RNAs. To determine if toxic CUG RNAs perturb choroid plexus functions, alternative splicing analysis was performed on lateral and hindbrain choroid plexi from Dmpk CTG knockin mice. Choroid plexus transcriptome-wide changes were evaluated in Mbnl2 knockout mice, a developmental-onset model of myotonic dystrophy brain dysfunction. To determine if transcriptome changes also occurred in the human disease, we obtained post-mortem choroid plexus for RNA-seq from donors without neurologically unaffected (two females, three males; ages 50-70) and myotonic dystrophy type 1 donors (one female, three males; ages 50-70). To test that choroid plexus transcriptome alterations resulted in altered CSF composition, we obtained CSF via lumbar puncture from patients with myotonic dystrophy type 1 (five females, five males; ages 35-55) and non-myotonic dystrophy patients (three females, four males; ages 26-51) and Western blot and osmolarity analyses were used to test CSF alterations predicted by choroid plexus transcriptome analysis. We determined that CUG RNA induced toxicity was more robust in the lateral choroid plexus of Dmpk CTG knockin mice due to comparatively higher Dmpk and lower Mbnl RNA levels. Impaired transitions to adult splicing patterns during choroid plexus development were identified in Mbnl2 knockout mice, including mis-splicing previously found in Dmpk CTG knockin mice. Whole transcriptome analysis of myotonic dystrophy type 1 choroid plexus revealed disease-associated RNA expression and mis-splicing events. Based on these RNA changes, predicted alterations in ion homeostasis, secretory output, and CSF composition were confirmed by analysis of myotonic dystrophy type 1 CSF. Our results implicate choroid plexus spliceopathy and concomitant alterations in CSF homeostasis as an unappreciated contributor to myotonic dystrophy type 1 CNS pathogenesis.
Project description:Misregulated alternative splicing appears to be a major factor in the pathogenesis of myotonic dystrophy. The present study was done to further explore alternative splicing in this condition by doing exon-level analysis of mRNA from skeletal muscle of 8 subjects with type 1 myotonic dystrophy, 7 subjects with type 2 myotonic dystrophy, 8 disease controls (subjects with facioscapulohumeral muscular dystrophy), and 8 healthy controls . The ratios of signals from the various exons of a gene provided an index of altered exon inclusion/exclusion that was independent of the overall expression of that gene. There were numerous transcripts for which there was evidence of abnormal alternative splicing in subjects with myotonic dystrophy. For many of these transcripts, the abnormal splicing was confirmed by an independent RT-PCR approach. 31 subjects, one sample per subject, four groups: healthy subjects (n = 8), facioscapulohumeral dystrophy (n = 8), type 1 myotonic dystrophy (n = 8), type 2 myotonic dystrophy (n = 7)
Project description:Autopsy and biopsy muscle and heart tissue was collected from consented human subjects with and without confirmed myotonic dystrophy type 1, myotonic dystrophy type 2, or Duchenne muscular dystrophy. RNA was isolated for preparation of RNAseq libraries and sequenced on the Illumina platform.
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Myotonic dystrophy type 1 (DM1) is a severe multisystemic disorder mediated by toxic RNA and abnormal RNA processing. Although splicing defects can explain some key disease symptoms, important gaps exist in our understanding of brain pathology, impeding the rational development of therapies. Here we investigated the different impact of DM1 on astrocytes, using a transgenic mouse model that expresses DM1-associated toxic CUG repeats-containing RNA. RNA sequencing revealed critical missplicing in transcripts that regulate cell adhesion, cytoskeleton and morphogenesis specific to astrocytes. These defects correlated with functional abnormalities in the assembly of focal adhesions and migration in culture, as well as defective astrocyte ramification and reorientation in vivo. Our results demonstrate that DM1 is critically deleterious for the adhesion and morphogenesis of astrocytes, possibly compromising the support and regulation of synaptic function .