Unknown,Transcriptomics,Genomics,Proteomics

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Complex Balanced Translocation Disrupting TCF4 and Altering TCF4 Isoform Expression Segregates as Mild Autosomal Dominant Intellectual Disability

ABSTRACT: Mutations of TCF4, which encodes a basic helix-loop-helix transcription factor, cause Pitt-Hopkins syndrome (PTHS) via multiple genetic mechanisms. TCF4 is a complex locus expressing multiple transcripts by alternative splicing and use of multiple promoters. We report a three-generation family segregating mild intellectual disability with an apparently balanced chromosomal translocation t(14;18)(q23.3;q21.2) that we characterized as a complex unbalanced karyotype 46,XY,der(14)del(14)(q23.3q23.3)t(14;18)(q23.3;q21.2)del(18)(q21.2q21.2) del(18)(q21.2q21.2)inv(18)(q21.2q21.2),der(18)t(14 ;18)(q23.3;q21.2) disrupting TCF4. Using whole genome sequencing, transcriptome sequencing, qRT-PCR and nCounter analysis, we characterized the breakpoint junctions from derivative chromosomes and gene expression at the TCF4 locus. Our analyses revealed that family members segregating mild intellectual disability with the complex chromosome aberration had normal expression of genes along chromosomes 14 or 18 and no marked changes in expression of genes other than TCF4. Affected individuals had 12-33 fold higher mRNA levels of TCF4 than did unaffected controls or individuals with PTHS. Increased levels of TCF4 transcript variants originating distal to the translocation breakpoint, not the fusion transcript generated by the derivative chromosome, contributed to this increased. Although validation in additional patients is required, our findings suggest that the dysmorphic features and severe intellectual disability characteristic of PTHS is partially rescued by overexpression of short TCF4 transcripts encoding a nuclear localization signal, a transcription activation domain, and the basic helix-loop-helix domain. Examination of TCF4 Isoform expression comparison between mutant and control skin fibroblast tissues

ORGANISM(S): Homo sapiens

SUBMITTER: Barbara Pusey

PROVIDER: E-GEOD-77742 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Polyamines are aliphatic polycations that have emerged as important determinants of cell growth and viability in rapidly proliferating cells, including in the pathogenic protozoan parasite Leishmania donovani. In L. donovani, the polyamine spermidine is synthesized by the successive conversion of ornithine into putrescine (catalyzed by ornithine decarboxylase or ODC) and putrescine into spermidine (catalyzed by spermidine synthase or SPDSYN). Deletion of either ODC (del-odc) or SPDSYN (del-spdsyn) from the L. donovani genome renders these parasites auxotrophic for polyamines and these mutants are impaired in their ability to survive both in culture and within the mammalian host without the addition of exogenous polyamine supplementation. Significantly, del-odc parasites immediately cease proliferation after putrescine is removed from the culture media and perish within two weeks, while spermidine starved del-spdsyn mutants, which retain intracellular putrescine pools, show a slow-growth phenotype, and persist for several weeks in culture. To elucidate the key differences within the proteome of putrescine-starved del-odc cells and spermidine-starved del-spdsyn parasites, a shotgun quantitative proteomics approach was undertaken using TMT labeling and LC-MS/MS analysis. Briefly, three biological replicates each for mid-log phase del-odc and del-spdsyn promastigotes grown in the presence of exogenous putrescine (for del-odc) or spermidine (for del-spdsyn) supplementation were washed to remove the exogenous polyamine supplementation and incubated in polyamine-free media. At 24 and 48 h, cells from each biological replicate were isolated and prepared for tandem mass tag (TMT) labeling and downstream LC-MS/MS analyses. Peptides were identified using a database generated from the reference genome of L. donovani BPK282A1 strain. Changes in relative protein abundance for the polyamine-starved del-odc and del-spdsyn cell lines at 24 and 48 h were calculated by comparing aggregate total reporter ion intensities for each protein to that of the corresponding polyamine-supplemented 0-h timepoint.

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Complex Balanced Translocation Disrupting TCF4 and Altering TCF4 Isoform Expression Segregates as Mild Autosomal Dominant Intellectual Disability

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