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MSTPublications: May 2021

Posted by on Monday, May 24, 2021 in New Publications .

Safety and efficacy of genetic MECP2 supplementation in the R294X mouse model of Rett syndrome.

Collins BE, Merritt JK, Erickson KR, Neul JL.
Genes Brain Behav. 2021 May 3:e12739. doi: 10.1111/gbb.12739. Online ahead of print.
PMID: 33942492

Rett syndrome is a neurodevelopmental disorder caused predominantly by loss-of-function mutations in MECP2, encoding transcriptional modulator methyl-CpG-binding protein 2 (MeCP2). Although no disease-modifying therapies exist at this time, some proposed therapeutic strategies aim to supplement the mutant allele with a wild-type allele producing typical levels of functional MeCP2, such as gene therapy. Because MECP2 is a dosage-sensitive gene, with both loss and gain of function causing disease, these approaches must achieve a narrow therapeutic window to be both safe and effective. While MeCP2 supplementation rescues RTT-like phenotypes in mouse models, the tolerable threshold of MeCP2 is not clear, particularly for partial loss-of-function mutations. We assessed the safety of genetically supplementing full-length human MeCP2 in the context of the R294X allele, a common partial loss-of-function mutation retaining DNA-binding capacity. We assessed the potential for adverse effects from MeCP2 supplementation of a partial loss-of-function mutant and the potential for dominant negative interactions between mutant and full-length MeCP2. In male hemizygous R294X mice, MeCP2 supplementation rescued RTT-like behavioral phenotypes and did not elicit behavioral evidence of excess MeCP2. In female heterozygous R294X mice, RTT-specific phenotypes were similarly rescued. However, MeCP2 supplementation led to evidence of excess MeCP2 activity in a motor coordination assay, suggesting that the underlying motor circuitry is particularly sensitive to MeCP2 dosage in females. These results show that genetic supplementation of full-length MeCP2 is safe in males and largely so females. However, careful consideration of risk for adverse motor effects may be warranted for girls and women with RTT.


Autism-Associated Variant in the SLC6A3 Gene Alters the Oral Microbiome and Metabolism in a Murine Model.
DiCarlo GE, Mabry SJ, Cao X, McMillan C, Woynaroski TG, Harrison FE, Reddy IA, Matthies HJG, Flynn CR, Wallace MT, Wu H, Galli A.
Front Psychiatry. 2021 Apr 15;12:655451. doi: 10.3389/fpsyt.2021.655451. eCollection 2021.
PMID: 33935841

Background: Altered dopamine (DA) signaling has been associated with autism spectrum disorder (ASD), a neurodevelopmental condition estimated to impact 1 in 54 children in the United States. There is growing evidence for alterations in both gastrointestinal function and oral microbiome composition in ASD. Recent work suggests that rare variants of the SLC6A3 gene encoding the DA transporter (DAT) identified in individuals with ASD result in structural and functional changes to the DAT. One such recently identified de novo mutation is a threonine to methionine substitution at position 356 of the DAT (DAT T356M). The DAT T356M variant is associated with ASD-like phenotypes in mice homozygous for the mutation (DAT T356M+/+), including social deficits, hyperactivity, and impaired DA signaling. Here, we determine the impact of this altered DA signaling as it relates to altered oral microbiota, and metabolic and gastrointestinal dysfunction. Methods: In the DAT T356M+/+ mouse, we determine the oral microbiota composition, metabolic function, and gastrointestinal (GI) function. We examined oral microbiota by 16S RNA sequencing. We measured metabolic function by examining glucose tolerance and we probed gastrointestinal parameters by measuring fecal dimensions and weight. Results: In the DAT T356M+/+ mouse, we evaluate how altered DA signaling relates to metabolic dysfunction and altered oral microbiota. We demonstrate that male DAT T356M+/+ mice weigh less (Wild type (WT) = 26.48 ± 0.6405 g, DAT T356M+/+ = 24.14 ± 0.4083 g) and have decreased body fat (WT = 14.89 ± 0.6206%, DAT T356M+/+ = 12.72 ± 0.4160%). These mice display improved glucose handling (WT = 32.60 ± 0.3298 kcal/g, DAT T356M+/+ = 36.97 ± 0.4910 kcal/g), and an altered oral microbiota. We found a significant decrease in Fusobacterium abundance. The abundance of Fusobacterium was associated with improved glucose handling and decreased body fat. Conclusions: Our findings provide new insights into how DAT dysfunction may alter gastrointestinal function, composition of the oral microbiota, and metabolism. Our data suggest that impaired DA signaling in ASD is associated with a number of metabolic and gastrointestinal changes which are common in individuals with ASD.


Multi-omic analysis elucidates the genetic basis of hydrocephalus.

Hale AT, Bastarache L, Morales DM, Wellons JC 3rd, Limbrick DD Jr, Gamazon ER.
Cell Rep. 2021 May 4;35(5):109085. doi: 10.1016/j.celrep.2021.109085.
PMID: 33951428

We conducted PrediXcan analysis of hydrocephalus risk in ten neurological tissues and whole blood. Decreased expression of MAEL in the brain was significantly associated (Bonferroni-adjusted p < 0.05) with hydrocephalus. PrediXcan analysis of brain imaging and genomics data in the independent UK Biobank (N = 8,428) revealed that MAEL expression in the frontal cortex is associated with white matter and total brain volumes. Among the top differentially expressed genes in brain, we observed a significant enrichment for gene-level associations with these structural phenotypes, suggesting an effect on disease risk through regulation of brain structure and integrity. We found additional support for these genes through analysis of the choroid plexus transcriptome of a murine model of hydrocephalus. Finally, differential protein expression analysis in patient cerebrospinal fluid recapitulated disease-associated expression changes in neurological tissues, but not in whole blood. Our findings provide convergent evidence highlighting the importance of tissue-specific pathways and mechanisms in the pathophysiology of hydrocephalus.


Colon epithelial cell TGFβ signaling modulates the expression of tight junction proteins and barrier function in mice

Smith PM, Choksi YA, Markham NO, Hanna DN, Zi J, Weaver CJ, Hamaamen JA, Lewis KB, Yang J, Liu Q, Kaji I, Means AL, Beauchamp DR.
Am J Physiol Gastrointest Liver Physiol. 2021 Jun 1;320(6):G936-G957. doi: 10.1152/ajpgi.00053.2021. Epub 2021 Mar 24.
PMID: 33759564

Defective barrier function is a predisposing factor in inflammatory bowel disease (IBD) and colitis-associated cancer (CAC). Although TGFβ signaling defects have been associated with IBD and CAC, few studies have examined the relationship between TGFβ and intestinal barrier function. Here, we examine the role of TGFβ signaling via SMAD4 in modulation of colon barrier function. The Smad4 gene was conditionally deleted in the intestines of adult mice and intestinal permeability assessed using an in vivo 4 kDa FITC-Dextran (FD4) permeability assay. Mouse colon was isolated for gene expression (RNA-sequencing), Western blot, and immunofluorescence analysis. In vitro colon organoid culture was utilized to assess junction-related gene expression by qPCR and transepithelial resistance (TER). In silico analyses of human IBD and colon cancer databases were performed. Mice lacking intestinal expression of Smad4 demonstrate increased colonic permeability to FD4 without gross mucosal damage. mRNA/protein expression analyses demonstrate significant increases in Cldn2/Claudin 2 and Cldn8/Claudin 8, and decreases in Cldn3, Cldn4, and Cldn7/Claudin 7 with intestinal SMAD4 loss in vivo without changes in Claudin protein localization. TGFβ1/BMP2 treatment of polarized SMAD4+ colonoids increases TER. Cldn2, Cldn4, Cldn7, and Cldn8 are regulated by canonical TGFβ signaling, and TGFβ-dependent regulation of these genes is dependent on nascent RNA transcription (Cldn2, Cldn4, Cldn8) but not nascent protein translation (Cldn4, Cldn8). Human IBD/colon cancer specimens demonstrate decreased SMAD4, CLDN4, CLDN7, and CLDN8 and increased CLDN2 compared with healthy controls. Canonical TGFβ signaling modulates the expression of tight junction proteins and barrier function in mouse colon.NEW & NOTEWORTHY We demonstrate that canonical TGFβ family signaling modulates the expression of critical tight junction proteins in colon epithelial cells, and that expression of these tight junction proteins is associated with maintenance of colon epithelial barrier function in mice.

Progesterone promotes immunomodulation and tumor development in the murine mammary gland.
Werner LR, Gibson KA, Goodman ML, Helm DE, Walter KR, Holloran SM, Trinca GM, Hastings RC, Yang HH, Hu Y, Wei J, Lei G, Yang XY, Madan R, Molinolo AA, Markiewicz MA, Chalise P, Axelrod ML, Balko JM, Hunter KW, Hartman ZC, Lange CA, Hagan CR.
J Immunother Cancer. 2021 May;9(5):e001710. doi: 10.1136/jitc-2020-001710.
PMID: 33958486

DebarcodeR Increases Fluorescent Cell Barcoding Capacity and Accuracy.
Reisman BJ, Barone SM, Bachmann BO, Irish JM.
Cytometry A. 2021 May 7. doi: 10.1002/cyto.a.24363. Online ahead of print.
PMID: 33960644

Germline risk of clonal haematopoiesis.
Silver AJ, Bick AG, Savona MR.
Nat Rev Genet. 2021 May 13. doi: 10.1038/s41576-021-00356-6. Online ahead of print.
PMID: 33986496 Review.

Structural and Functional Imaging of the Retina in Central Retinal Artery Occlusion – Current Approaches and Future Directions.
Mac Grory B, Schrag M, Poli S, Boisvert CJ, Spitzer MS, Schultheiss M, Nedelmann M, Yaghi S, Guhwe M, Moore EE, Hewitt HR, Barter KM, Kim T, Chen M, Humayun L, Peng C, Chhatbar PY, Lavin P, Zhang X, Jiang X, Raz E, Saidha S, Yao J, Biousse V, Feng W.
J Stroke Cerebrovasc Dis. 2021 May 16;30(7):105828. doi: 10.1016/j.jstrokecerebrovasdis.2021.105828. Online ahead of print.
PMID: 34010777 Review.

Visual Influences on Auditory Behavioral, Neural, and Perceptual Processes: A Review.
Opoku-Baah C, Schoenhaut AM, Vassall SG, Tovar DA, Ramachandran R, Wallace MT.
J Assoc Res Otolaryngol. 2021 May 20. doi: 10.1007/s10162-021-00789-0. Online ahead of print.
PMID: 34014416 Review.