Alternative Splicing

Mutations in SF3B1, which encodes a spliceosome component, are associated with poor outcome in chronic lymphocytic leukemia (CLL), but how these contribute to CLL progression remains poorly understood. We undertook a transcriptomic characterization of primary human CLL cells to identify transcripts and pathways affected by SF3B1 mutation. Splicing alterations, identified in the analysis of bulk cells, were confirmed in single SF3B1-mutated CLL cells and also found in cell lines ectopically expressing mutant SF3B1. SF3B1 mutation was found to dysregulate multiple cellular functions including DNA damage response, telomere maintenance, and Notch signaling (mediated through KLF8 upregulation, increased TERC and TERT expression, or altered splicing of DVL2 transcript, respectively). SF3B1 mutation leads to diverse changes in CLL-related pathways.

Neurofibromatosis type I (Nf1) is a GTPase-activating protein (GAP) that inactivates the oncoprotein Ras and plays important roles in nervous system development and learning. Alternative exon 23a falls within the Nf1 GAP domain coding sequence and is tightly regulated in favor of skipping in neurons; however, its biological function is not fully understood. Here we generated mouse embryonic stem (ES) cells with a constitutive endogenous Nf1 exon 23a inclusion, termed Nf1 23aIN/23aIN cells, by mutating the splicing signals surrounding the exon to better match consensus sequences. We also made Nf1 23aΔ/23aΔ cells lacking the exon. Active Ras levels are high in wild-type (WT) and Nf1 23aIN/23aIN ES cells, where the Nf1 exon 23a inclusion level is high, and low in Nf1 23aΔ/23aΔ cells. Upon neuronal differentiation, active Ras levels are high in Nf1 23aIN/23aIN cells, where the exon inclusion level remains high, but Ras activation is low in the other two genotypes, where the exon is skip...

The Drosophila polypyrimidine tract-binding protein (dmPTB or hephaestus) plays an important role during embryogenesis. A loss of function mutation, heph(03429), results in varied defects in embryonic developmental processes, leading to embryonic lethality. However, the suite of molecular functions that are disrupted in the mutant remains unknown. We have used an unbiased high throughput sequencing approach to identify transcripts that are misregulated in this mutant. Misregulated transcripts show evidence of significantly altered patterns of splicing (exon skipping, 5' and 3' splice site switching), alternative 5' ends, and mRNA level changes (up and down regulation). These findings are independently supported by reverse-transcription-polymerase chain reaction (RT-PCR) analysis and in situ hybridization. We show that a group of genes, such as Zerknüllt, z600 and screw are among the most upregulated in the mutant and have been functionally linked to dorso-ventral pattern...

We reported previously that human geneMAGE-1 directs the expression of a tumor antigen recognized on a melanoma by autologous cytolytic T lymphocytes. Probing cosmid libraries with aMAGE-1 sequence, we identified 11 closely related genes. The analysis of hamster-human somatic cell hybrids indicated that the 12MAGE genes are located in the q terminal region of chromosome X. LikeMAGE-1, the 11 additionalMAGE genes have their entire coding sequence located in the last exon, which shows 64%-85% identity with that ofMAGE-1. The coding sequences of theMAGE genes predict the same main structural features for allMAGE proteins. In contrast, the promoters and first exons of the12 MAGE genes show considerable variability, suggesting that the existence of this gene family enables the same function to be expressed under different transcriptional controls. The expression of eachMAGE gene was evaluated by reverse transcription and polymerase chain reaction amplification. Six genes of theMAGE family includingMAGE-1 were found to be expressed at a high level in a number of tumors of various histological types. None was expressed in a large panel of healthy tissues, with the exception of testis and placenta.

Barley (Hordeum vulgare L.) is among the world's earliest domesticated and most important crop plants. It is diploid with a large haploid genome of 5.1 gigabases (Gb). Here we present an integrated and ordered physical, genetic and functional sequence resource that describes the barley gene-space in a structured whole-genome context. We developed a physical map of 4.98 Gb, with more than 3.90 Gb anchored to a high-resolution genetic map. Projecting a deep whole-genome shotgun assembly, complementary DNA and deep RNA ...

N-methyl-d-aspartate receptors (NMDARs) are present at many excitatory glutamate synapses in the central nervous system and display unique properties that depend on their subunit composition. Biophysical, pharmacological and molecular methods have been used to determine the key features conferred by the various NMDAR subunits, and have helped to establish which NMDAR subtypes are present at particular synapses. Recent studies are

HUVEC or mouse 3T3 cells infected with SV-40 generate within 3 to 5 days post-infection an ENOX2 species corresponding to the exon-4 minus splice variant of a tumor-associated NADH oxidase (ENOX2 or tNOX) expressed at the cancer cell surface. This study was to seek evidence for splicing factors that might direct formation of the exon 4 minus ENOX2 splice variant. To determine if silencing of ENOX2 exon 4 occurs because of motifs located in exon 4, transfections were performed on MCF-10A (mammary non-cancer), BT-20 (mammary cancer), and HeLa (cervical cancer) cells using a GFP minigene construct containing either a constitutively spliced exon (albumin exon 2) or the alternatively spliced ENOX2 exon 4 between the two GFP halves. Removal of exon 4 from the processed RNA of the GFP minigene construct occurred with HeLa and to a lesser extent with BT-20 but not in non-cancer MCF-10A cells. The Splicing Rainbow Program was used to identify all of the possible hnRNPs binding sites of exon 4 of ENOX2. There are 8 Exonic Splicing Silencers (ESSs) for hnRNP binding in the exon 4 sequences. Each of these sites were mutated by site-directed mutagenesis to test if any were responsible for the splicing skip. Results showed MutG75 ESS mutation changed the GFP expression which is a sign of splicing silence, while other mutations did not. As MutG75 changed the ESS binding site for hnRNP F, this result suggests that hnRNP F directs formation of the exon 4 minus variant of ENOX2.

Cystic fibrosis (CF) is the most common fatal autosomal recessive multisystem disorder, which occurs mainly in European-derived populations. The incidence of CF varies between 1 in 2000 to 3000 live-births in various ethnic groups. The disease is rare in East Asians. Here we report a 9 year old Thai male patient, who was diagnosed to have CF based on recurrent pneumonia, a slow weight gain, pancreatic insufficiency and repeatedly elevated sweat chloride levels by two different methods. A comprehensive genetic analysis showed the splicing mutation, 1898+ 1G-->T, which was apparently of maternal origin. Literature search found 39 documented cases of CF patients in East Asians. CFTR (MIM# 602421) genotyping was performed in 14 patients including our patient and in 9 of them a CF allele was identified. The findings seem to indicate that the splicing mutations, 1898+ 1G-->T and 1898+ 5G-->T are more common in East Asian CF patients.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant genetic disorder caused by mutations in the NF1 gene. In this paper we report our experience using the cDNA-SSCP/HD analysis as a mutational screening approach and the double characterization of all mutations at the DNA and RNA levels. Two hundred and eighty-two different mutations (in 374 independent patients) were identified, 140 of which were novel in our population. Most of these mutations are unique and distributed along the gene. However, we also detected 37 recurrent mutations. Our approach is limited with respect to the detection of single base substitutions, but it is highly effective in the detection of frameshift mutations and mutations that affect the correct splicing. Due to this bias we focus here in the characterization of these two types of mutations. Forty-seven percent of mutations found were frameshift mutations, with small deletions being 2.3 times more common than small insertions. At the mRNA level, 44% of mutations affected the correct splicing, 80% of them located in the consensus sequences, with the donor site being much more frequently involved. The remaining 20% consisted of mutations located in deep intronic sites and mutations located in the coding region. In general the latter group produces different types of mutated transcripts with specific proportions for each mutation. The double characterization of mutations at the DNA and RNA levels enables to detect a broader spectrum of mutations than any single level approach, and provides a greater understanding of their molecular pathogenesis. © 2008 Wiley-Liss, Inc.

We report the results of a transcript finishing initiative, undertaken for the purpose of identifying and characterizing novel human transcripts, in which RT-PCR was used to bridge gaps between paired EST clusters, mapped against the genomic sequence. Each pair of EST clusters selected for experimental validation was designated a transcript finishing unit (TFU). A total of 489 TFUs were selected for validation, and an overall efficiency of 43.1% was achieved. We generated a total of 59,975 bp of transcribed sequences organized into 432 exons, contributing to the definition of the structure of 211 human transcripts. The structure of several transcripts reported here was confirmed during the course of this project, through the generation of their corresponding full-length cDNA sequences. Nevertheless, for 21% of the validated TFUs, a full-length cDNA sequence is not yet available in public databases, and the structure of 69.2% of these TFUs was not correctly predicted by computer prog...