Exon 1A Research Articles

Epigenetic Activation of BRCA1 by Genistein In Vivo and Triple Negative Breast Cancer Cells Linked to Antagonism toward Aryl Hydrocarbon Receptor.

Triple negative breast cancers (TNBC) are the most aggressive and lethal breast cancers (BC). The aryl hydrocarbon receptor (AHR) is often overexpressed in TNBC, and its activation results in the epigenetic silencing of BRCA1, which is a necessary factor for the transcriptional activation of estrogen receptor (ER)α. The dietary isoflavone genistein (GEN) modulates BRCA1 CpG methylation in BC cells. The purpose of this study was to investigate the effect of GEN on BRCA1 epigenetic regulation and AHR activity in vivo and TNBC cells. Mice were administered a control or GEN-enriched (4 and 10 ppm) diet from gestation through post-natal day 50. Mammary tissue was analyzed for changes in BRCA1 regulation and AhR activity. TNBC cells with constitutively hypermethylated BRCA1 (HCC38) and MCF7 cells were used. Protein levels and mRNA expression were measured by Western blot and real-time PCR, respectively. BRCA1 promoter occupancy and CpG methylation were analyzed by chromatin immunoprecipitation and methylation-specific PCR, respectively. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. GEN administered in the diet dose-dependently decreased basal Brca1 methylation and AHR activity in the mammary gland of adult mice. HCC38 cells were found to overexpress constitutively active AHR in parallel with BRCA1 hypermethylation. The treatment of HCC38 cells with GEN upregulated BRCA1 protein levels, which was attributable to decreased CpG methylation and AHR binding at BRCA1 exon 1a. In MCF7 cells, GEN prevented the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-dependent localization of AHR at the BRCA1 gene. These effects were consistent with those elicited by control AHR antagonists galangin (GAL), CH-223191, and α-naphthoflavone. The pre-treatment with GEN sensitized HCC38 cells to the antiproliferative effects of 4-hydroxytamoxifen. We conclude that the dietary compound GEN may be effective for the prevention and reversal of AHR-dependent BRCA1 hypermethylation, and the restoration of ERα-mediated response, thus imparting the sensitivity of TNBC to antiestrogen therapy.

SRSF1-dependent alternative splicing attenuates BIN1 expression in non-small cell lung cancer.

Decreased bridging integrator 1 (BIN1) expression has great significance in promoting the progression of malignant tumors. Reduced messenger RNA expression is partly due to aberrant alternative splicing (AS). However, the AS status of BIN1 and its correlation with BIN1 inactivation in non-small cell lung cancer (NSCLC) remains poorly defined. Here we reported that BIN1 inactivation was not related to DNA methylation in NSCLC. Importantly, BIN1 with exon 12A inclusion (BIN1+12A isoform), the most frequent aberrant splicing variant in tumors was also observed in NSCLC, and might be accounted for BIN1 inactivation. Furthermore, we showed that the aberrant splicing of BIN1 was under the control of serine and arginine-rich factor 1 (SRSF1) in NSCLC. In addition, colony formation assay showed that BIN1+12A isoform could abolish the tumor-inhibiting ability of BIN1 in NSCLC cells. Meanwhile, transwell, wound healing and apoptosis experiments demonstrated that theoccurrence of BIN1+12A could abrogate the invasion suppressing activity and proapoptotic property of BIN1 in NSCLC. Significantly, we also found that BIN1+12A isoform neutralized the tumor-suppressing functions of BIN1 via affecting its subcellular localization. Altogether, these data revealed an aberrant splicing phenomenon which abated the expression and tumor-inhibiting activity of BIN1 in NSCLC, and the related mechanisms were associated with SRSF1.

Tissue- and cell-specific expression of a splice variant in the II-III cytoplasmic loop of Cacna1b.

Presynaptic CaV2.2 (N‐type) channels are fundamental for transmitter release across the nervous system. The gene encoding CaV2.2 channels, Cacna1b, contains alternatively spliced exons that result in functionally distinct splice variants (e18a, e24a, e31a, and 37a/37b). Alternative splicing of the cassette exon 18a generates two mRNA transcripts (+e18a‐Cacna1b and ∆e18a‐Cacna1b). In this study, using novel mouse genetic models and in situ hybridization (BaseScope™), we confirmed that +e18a‐Cacna1b splice variants are expressed in monoaminergic regions of the midbrain. We expanded these studies and identified +e18a‐Cacna1b mRNA in deep cerebellar cells and spinal cord motor neurons. Furthermore, we determined that +e18a‐Cacna1b is enriched in cholecystokinin‐expressing interneurons. Our results provide key information to understand cell‐specific functions of CaV2.2 channels.

Thermal unfolding of various human non-muscle isoforms of tropomyosin

Tropomyosin (Tpm) is an α-helical coiled-coil protein dimer, which forms a continuous head-to-tail polymer along the actin filament. In striated muscles, Tpm plays an important role in the Ca2+-dependent regulation of muscle contraction. However, little is known about functional and especially structural properties of the numerous non-muscle Tpm isoforms. In the present work, we have applied circular dichroism (CD) and differential scanning calorimetry (DSC) to investigate thermal unfolding and domain structure of various non-muscle human Tpm isoforms. These isoforms, the products of two different genes, TPM1 and TPM3, also significantly differ by alternatively spliced exons: N-terminal exons 1a2b or 1b, internal exons 6a or 6b, and C-terminal exons 9a, 9c or 9d. Our results clearly demonstrate that structural properties of various non-muscle Tpm isoforms can be quite different depending on the presence of different alternatively spliced exons in their genes. These data show for the first time a significant difference in the thermal unfolding between muscle and non-muscle Tpm isoforms and indicate that replacement of alternatively spliced exons alters the stability of certain domains in the Tpm molecule.

SUN-510 Pseudohypoparathyroidism Type 1b Presenting With Fahr Syndrome In An Adolescent.

Background: Fahr syndrome is a condition characterized by the presence of abnormal calcifications in the basal ganglia and cerebral cortex, and has been linked with parathyroid disorders. We report a case of pseudohypoparathyroidism (PHP) type 1b in an adolescent presenting with recurrent seizures and intracranial calcifications. Clinical Case: A 15-year old boy presented with recurrent seizures that were uncontrolled despite treatment with anti-epileptic medications. He was diagnosed with epilepsy at the age of 9 overseas and had also been started on levothyroxine 25 mcg daily for hypothyroidism. He arrived in the US for further evaluation and management. He was initially seen by pediatric neurology wherein lab work-up showed hypocalcemia with a total calcium of 6.6 mg/dL (n 8.5-10.5). CT scan of the brain showed disseminated intracranial cortical and basal ganglia calcifications, consistent with Fahr syndrome. EEG showed generalized background slowing compatible with mild diffuse cerebral dysfunction. He was referred to pediatric endocrinology. At his endocrine visit, growth parameters were normal with height at 81st percentile, weight at 88th percentile, and BMI at 84th percentile. Family history was negative of seizures, thyroid or calcium disorders. He does not have intellectual disability. Physical exam did not reveal any features of Albright hereditary osteodystrophy. Additional lab testing showed ionized calcium 0.79 mmol/L (n 1.1-1.35), phosphorus 8.7 mg/dL (n 2.9-5.1), PTH 439 pg/mL (n 10.0-65.0), alkaline phosphatase (ALP) 308 U/L (n 60-270) and 25-hydroxy vitamin D 25.8 ng/mL (n 30-83). Renal function was normal. Findings were suggestive of PTH resistance. Thyroid function showed TSH 4.74 uU/mL (n 0.4-4.6), free T4 1.15 ng/dL (n 0.8-1.7) and negative thyroid antibodies (TPO, TG), suggestive of partial TSH resistance. He was treated with calcium carbonate, calcitriol and ergocalciferol. Levothyroxine was continued. Genetic testing was done which showed a partial loss of methylation in the GNAS exon 1A locus (patient 28%, [normal methylation ≥44%, complete loss of methylation ≤ 12%]), confirming the diagnosis of PHP type 1b. Calcium, phosphorus and ALP levels subsequently normalized with calcium and vitamin D supplementation. PTH improved though remains to be elevated (PTH 67.9 pg/mL). Anti-epileptic medications were weaned off after being seizure-free for more than 2 years. Conclusion: In this case, our patient presented with a distinct triad of epileptic seizure, extensive brain calcification, and hypocalcemia. This clinical scenario should prompt diagnostic evaluation for PHP as a treatable cause of epileptic seizures in children. Genetic testing for PHP type 1b showed partial loss of methylation in the GNAS locus, which was sufficient to cause disease.

Characterizing the Alternative Splicing Dynamics of Cav1.3, a Calcium Ion Channel Involved in Autism Spectrum Disorder

Voltage‐gated calcium channels move calcium ions across cellular membranes in response to action potential stimuli, which mediate processes including cellular signaling, neurotransmitter discharge, muscle contraction, and gene expression. They are multimer proteins composed of alpha‐1, beta, alpha‐2/delta, and gamma subunits. Variety in calcium channels is afforded by different subtypes of alpha‐1, including the A, B, C, D, E, and S isoforms.Cav1.3 is a member of the L‐type calcium channels and is categorized in the high‐voltage activated family. It employs the alpha‐1 subunit encoded by the CACNA1D gene. The alpha‐1 subunit forms four homologous repeat domains, each consisting of six transmembrane helical segments. Cacna1d knock out mice suffer from bradycardia and congenital deafness, testifying to the significance of the alpha‐1 subunit in the sinoatrial node and in auditory hair cells. Naturally occurring missense mutations in alternatively spliced regions of CACNA1D, such as the mutually exclusive exons 8a and 8b encoding part of the sixth transmembrane segment of domain I, have been reported to be gain‐of‐function mutations, which cause aldosterone‐producing adenomas, aldosteronism, seizures, and autism spectrum disorder, highlighting the importance of alternative splicing for Cav1.3 function.Although the diseases derived from CACNA1D mutations have been characterized, the splicing dynamics of the CACNA1D pre‐mRNA that gives rise to the different alpha‐1 isoforms is not well understood. Here, we describe the alternatively spliced isoforms of Cacna1d and their distribution in mouse tissues.Support or Funding InformationNational Institute of General Medical Sciences Grant 1R15GM119099‐01This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Multiple mutations in the nicotinic acetylcholine receptor Cc\u03b16 gene associated with resistance to spinosad in medfly

Spinosad is an insecticide widely used for the control of insect pest species, including Mediterranean fruit fly, Ceratitis capitata. Its target site is the α6 subunit of the nicotinic acetylcholine receptors, and different mutations in this subunit confer resistance to spinosad in diverse insect species. The insect α6 gene contains 12 exons, with mutually exclusive versions of exons 3 (3a, 3b) and 8 (8a, 8b, 8c). We report here the selection of a medfly strain highly resistant to spinosad, JW-100 s, and we identify three recessive Ccα6 mutant alleles in the JW-100 s population: (i) Ccα63aQ68* containing a point mutation that generates a premature stop codon on exon 3a (3aQ68*); (ii) Ccα63aAG>AT containing a point mutation in the 5′ splicing site of exon 3a (3aAG > AT); and (iii) Ccα63aQ68*-K352* that contains the mutation 3aQ68* and another point mutation on exon 10 (K352*). Though our analysis of the susceptibility to spinosad in field populations indicates that resistance has not yet evolved, a better understanding of the mechanism of action of spinosad is essential to implement sustainable management practices to avoid the development of resistance in field populations.

Cells exhibiting strong p16INK4a promoter activation in vivo display features of senescence.

The activation of cellular senescence throughout the lifespan promotes tumor suppression, whereas the persistence of senescent cells contributes to aspects of aging. This theory has been limited, however, by an inability to identify and isolate individual senescent cells within an intact organism. Toward that end, we generated a murine reporter strain by "knocking-in" a fluorochrome, tandem-dimer Tomato (tdTom), into exon 1α of the p16INK4a locus. We used this allele (p16tdTom ) for the enumeration, isolation, and characterization of individual p16INK4a -expressing cells (tdTom+). The half-life of the knocked-in transcript was shorter than that of the endogenous p16INK4a mRNA, and therefore reporter expression better correlated with p16INK4a promoter activation than p16INK4a transcript abundance. The frequency of tdTom+ cells increased with serial passage in cultured murine embryo fibroblasts from p16tdTom/+ mice. In adult mice, tdTom+ cells could be readily detected at low frequency in many tissues, and the frequency of these cells increased with aging. Using an in vivo model of peritoneal inflammation, we compared the phenotype of cells with or without activation of p16INK4a and found that tdTom+ macrophages exhibited some features of senescence, including reduced proliferation, senescence-associated β-galactosidase (SA-β-gal) activation, and increased mRNA expression of a subset of transcripts encoding factors involved in SA-secretory phenotype (SASP). These results indicate that cells harboring activation of the p16INK4a promoter accumulate with aging and inflammation in vivo, and display characteristics of senescence.

Platelet-derived growth factor receptor α gene is regulated by multiple first exons

Transcription of the platelet-derived growth factor receptor α (PDGFRA/Pdgfra) gene is considered to be precisely regulated. We have previously reported that the PDGFRA/Pdgfra gene is regulated by a dual promoter system in human and mouse, in which a novel PDGFRA/Pdgfra transcript has a first exon (exon 1β) different from that of the canonical PDGFRA/Pdgfra transcript (exon 1α). To elucidate the function of each transcript, we first investigated the contribution of different PDGFRA transcripts to final protein levels. Notably, knockdown experiments suggested the existence of other PDGFRA transcripts, and we identified five additional first exons (exons 1γ, 1δ, 1ε, 1ζ, and 1η) in intron 1 in both the human and mouse genes. The first exons of the mouse Pdgfra gene showed unique expression patterns: exon 1α was broadly expressed; exon 1β was highly expressed in embryos; exon 1γ was observed at relatively high levels in the adult central nervous system (CNS); and exon 1δ was expressed at relatively high levels in the developing CNS. Furthermore, in silico analysis of common putative transcription factor binding sites in the upstream regions of the first exons of both human and mouse PDGFRA/Pdgfra genes predicted common (such as Sry, Mzf1, and Cdx) and unique (such as Sox5, Lmo2, and GATA) transcription factors. Our findings show the diversity of the transcriptional regulation of the PDGFRA/Pdgfra gene.

All-trans retinoic acid suppresses bone morphogenetic protein 4 in mouse diabetic nephropathy through a unique retinoic acid response element.

Diabetic nephropathy (DN) causes mesangial matrix expansion, which results in glomerulosclerosis and renal failure. Collagen IV (COL4) is a major component of the mesangial matrix that is positively regulated by bone morphogenetic protein 4 (BMP4)/suppressor of mothers against decapentaplegic (Smad1) signaling. Because previous studies showed that retinoids treatment had a beneficial effect on kidney disease, we investigated the therapeutic potential of retinoids in DN, focusing especially on the regulatory mechanism of BMP4. Diabetes was induced with streptozotocin in 12-wk-old male Crl:CD1(ICR) mice, and, 1 mo later, we initiated intraperitoneal injection of all-trans retinoic acid (ATRA) three times weekly. Glomerular matrix expansion, which was associated with increased BMP4, phosphorylated Smad1, and COL4 expression, worsened in diabetic mice at 24 wk of age. ATRA administration alleviated DN and downregulated BMP4, phosopho-Smad1, and COL4. In cultured mouse mesangial cells, treatment with ATRA or a retinoic acid receptor-α (RARα) agonist significantly decreased BMP4 and COL4 expression. Genomic analysis suggested two putative retinoic acid response elements (RAREs) for the mouse Bmp4 gene. Chromatin immunoprecipitation analysis and reporter assays indicated a putative RARE of the Bmp4 gene, located 11,488-11,501 bp upstream of exon 1A and bound to RARα and retinoid X receptor (RXR), which suppressed BMP4 expression after ATRA addition. ATRA suppressed BMP4 via binding of a RARα/RXR heterodimer to a unique RARE, alleviating glomerular matrix expansion in diabetic mice. These findings provide a novel regulatory mechanism for treatment of DN.

Foetal 2:1 atrioventricular block in a patient with Timothy syndrome (LQT8) (RCDD code: VI-1B-1.2)

Long QT syndrome (LQTS) may be a cause of foetal bradyarrhythmia and an important cause of death in children with arrhythmia. We present the case of a patient of Kadazan Iban descent with LQTS. He was detected prenatally to have foetal 2:1 atrioventricular (AV) block and tetralogy of Fallot. His postnatal electrocardiogram revealed a functional 2:1 AV block with QTc interval of 690 ms. Dysmorphism and cutaneous syndactyly of both hands and feet pointed to a diagnosis of classical Timothy syndrome (TS) type 1. This diagnosis was confirmed molecularly with a heterozygous mutation c.1216G>A. p. (Gly406Arg) at exon 8A in the CACNA1C gene. To the best of our knowledge, this is the first reported case of TS in a Kadazan Iban child. JRCD 2019; 4 (2): 42-46.

Expression of murine muscle-enriched A-type lamin-interacting protein (MLIP) is regulated by tissue-specific alternative transcription start sites

Muscle-enriched lamin-interacting protein (Mlip) is an alternatively spliced gene whose splicing specificity is dictated by tissue type. MLIP is most abundantly expressed in brain, cardiac, and skeletal muscle. In the present study, we systematically mapped the transcriptional start and stop sites of murine Mlip Rapid amplification of cDNA ends (RACE) of Mlip transcripts from the brain, heart, and skeletal muscle revealed two transcriptional start sites (TSSs), exon 1a and exon 1b, and only one transcriptional termination site. RT-PCR analysis of the usage of the two identified TSSs revealed that the heart utilizes only exon 1a for MLIP expression, whereas the brain exclusively uses exon 1b TSS. Loss of Mlip exon 1a in mice resulted in a 7-fold increase in the prevalence of centralized nuclei in muscle fibers with the Mlip exon1a-deficient satellite cells on single fibers exhibiting a significant delay in commitment to a MYOD-positive phenotype. Furthermore, we demonstrate that the A-type lamin-binding domain in MLIP is encoded in exon 1a, indicating that MLIP isoforms generated with exon 1b TSS lack the A-type lamin-binding domain. Collectively these findings suggest that Mlip tissue-specific expression and alternative splicing play a critical role in determining MLIP's functions in mice.

Anti-angiogenic isoform of vascular endothelial growth factor-A in cardiovascular and renal disease.

Accumulating evidence suggests that pathologic interactions between the heart and the kidney can contribute to the progressive dysfunction of both organs. Recently, there has been an increase in the prevalence of cardiovascular disease (CVD) and chronic kidney disease (CKD) due to increasing obesity rates. It has been reported that obesity causes various heart and renal disorders and appears to accelerate their progression. Vascular endothelial growth factor-A (VEGF-A) is a major regulator of angiogenesis and vessel permeability, and is associated with CVD and CKD. It is now recognized that alternative VEGF-A gene splicing generates VEGF-A isoforms that differ in their biological actions. Proximal splicing that includes an exon 8a sequence results in pro-angiogenic VEGF-A165a, whereas distal splicing inclusive of exon 8b yields the anti-angiogenic isoform of VEGF-A (VEGF-A165b). This review highlights several recent preclinical and clinical studies on the role of VEGF-A165b in CVD and CKD as a novel function of VEGF-A. This review also discusses potential therapeutic approaches of the use of VEGF-A in clinical settings as a potential circulating biomarker for CVD and CKD.

Antisense oligonucleotides modulate dopa decarboxylase function in aromatic l-amino acid decarboxylase deficiency.

Aromatic l-amino acid decarboxylase deficiency (AADCD), attributed to mutations in the dopa decarboxylase (DDC) gene, is a rare neurometabolic disease resulting from a defect in the biosynthesis of dopamine and serotonin. The DDC c.714+4A>T mutation is the most prevalent mutation among patients with AADCD, and is also a founder mutation among Taiwanese patients. In this study, the molecular consequences and function of this mutation were examined in AADCD patient-derived lymphoblastoid cells. We identified novel DDC mRNA isoforms spliced with a new exon (exon 6a) in normal and c.714+4A>T lymphoblastoid cells. In addition, we identified the SR proteins (SRSF9 and SRSF6), as well as cis-elements involved in modulating the splicing of this mutated transcript. Notably, we demonstrated that antisense oligonucleotides (ASOs) were able to restore the normal mRNA splicing and increase the level of DDC protein, as well as its downstream product serotonin, in lymphoblastoid cells derived from the patient with AADCD, suggesting that these ASOs might represent a feasible alternative strategy for gene therapy of AADCD in patients with the common c.714+4A>T mutation.

CRISPR -Mediated Expression of the Fetal Scn5a Isoform in Adult Mice Causes Conduction Defects and Arrhythmias.

BackgroundThe sodium channel, Nav1.5, encoded by SCN5A, undergoes developmentally regulated splicing from inclusion of exon 6A in the fetal heart to exon 6B in adults. These mutually exclusive exons differ in 7 amino acids altering the electrophysiological properties of the Nav1.5 channel. In myotonic dystrophy type 1, SCN5A is mis‐spliced such that the fetal pattern of exon 6A inclusion is detected in adult hearts. Cardiac manifestations of myotonic dystrophy type 1 include conduction defects and arrhythmias and are the second‐leading cause of death.Methods and ResultsThis work aimed to determine the impact of SCN5A mis‐splicing on cardiac function. We used clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR‐associated protein 9 (Cas9) to delete Scn5a exon 6B in mice, thereby redirecting splicing toward exon 6A. These mice exhibit prolonged PR and QRS intervals, slowed conduction velocity, extended action potential duration, and are highly susceptible to arrhythmias.ConclusionsOur findings highlight a nonmutational pathological mechanism of arrhythmias and conduction defects as a result of mis‐splicing of the predominant cardiac sodium channel. Animals homozygous for the deleted exon express only the fetal isoform and have more‐severe phenotypes than heterozygotes that also express the adult isoform. This observation is directly relevant to myotonic dystrophy type 1, and possibly pathological arrhythmias, in which individuals differ with regard to the ratios of the isoforms expressed.

Rat enteric glial cells express novel isoforms of Interleukine-7 regulated during inflammation.

Neuroimmune interactions are essential to maintain gut homeostasis and prevent intestinal disorders but so far, the impact of enteric glial cells (EGC) on immune cells remains a relatively unexplored area of research. As a dysregulation of critical cytokines such as interleukine-7 (IL-7) was suggested to exacerbate gut chronic inflammation, we investigated whether EGC could be a source of IL-7 in the gastrointestinal tract. Expression of IL-7 in the rat enteric nervous system was analyzed by immunochemistry and Q-PCR. IL-7 variants were cloned and specific antibodies against rat IL-7 isoforms were raised to characterize their expression in the submucosal plexus. IL-7 isoforms were produced in vitro to analyze their impact on T-cell survival. Neurons and glial cells of the rat enteric nervous system expressed IL-7 at both mRNA and protein levels. Novel rat IL-7 isoforms with distinct C-terminal parts were detected. Three of these isoforms were found in EGC or in both enteric neurons and EGC. Exposure of EGC to pro-inflammatory cytokines (IL-1β and/or TNFα) induced an upregulation of all IL-7 isoforms. Interestingly, time-course and intensity of the upregulation varied according to the presence or absence of exon 5a in IL-7 variants. Functional analysis on T lymphocytes revealed that only canonical IL-7 protects T cells from cell death. IL-7 and its variants are expressed by neurons and glial cells in the enteric nervous system. Their distinct expression and upregulation in inflammatory conditions suggest a role in gut homeostasis which could be critical in case of chronic inflammatory diseases.

Association of growth hormone gene receptor polymorphism with production traits in Jamunapari goat

Genetic polymorphism for GHR gene was carried out in Jamunapari kids by Polymerase Chain Reaction- Restriction Fragment Length Polymorphism (PCR-RFLP). Blood samples were collected from 200 kids for isolation of genomic DNA. The exon 1A (210 bp fragment), exon 10 (342 bp fragment) and 5’ non-coding region (318 bp fragment) of GHR gene were amplified and digested with MspI, AluI and NsiI restriction endonuclease, respectively. PCR-RFLP analysis for 5’ non-coding region revealed monomorphic pattern while exon 1A and exon 10 of GHR were polymorphic. The frequency of A and T alleles was 0.54 and 0.46, respectively, and frequency of three genotypes (AA, AT and TT) was 0.17, 0.74 and 0.09, respectively at locus exon 1A of GHR. The frequency of A and G allele for exon 10 was 0.53 and 0.47, and frequency of three genotypes (AA, AG and GG) was 0.16, 0.74 and 0.10, respectively. The genotype AG was associated with higher body weights at different growth stages. The goats with AG genotype were heavier to AA and GG genotypes by 4.91 and 42.85% at birth; 8.59 and 13.30% at 6 months; 8.02 and 17.25% at 9 months and 7.11 and 16.11% at 12 months, respectively. The locus was also a significant source of variation for biometrical traits (body weight, body length, heart girth) at different ages. AG genotype could be used as marker in selection for higher body weights in Jamunapari goats.

Tissue-specific variation in 5ʹ-terminal exons of mouse Anoctamin 1 transcript induces N-terminal variation of its protein via alternative translational start sites

Anoctamin 1 (encoded by the Ano1 gene) is a Ca2+-activated Cl− channel critical to many physiological functions. It has been speculated that Ano1 expression is regulated in a tissue-dependent manner via alternative promoters. However, variation in the 5ʹ-end sequence of mouse Ano1 (mAno1) and its tissue-dependent regulation are poorly understood. We identified a novel 5ʹ-terminal exon (designated exon 1a) of mAno1 instead of the known 5ʹ-terminal exon (exon 0) using 5ʹ-rapid amplification of cDNA ends (RACE) analysis. Unexpectedly, the novel 5ʹ-end variant mAno1Ex1a was abundantly expressed in many tissues including the salivary and mammary glands, rectum, lung, trachea and prostate. In contrast, the known variant mAno1Ex0 predominated only in male reproductive tissues such as the epididymis and testis. In a heterologous expression system, mAno1Ex0 encoded a longer protein than mAno1Ex1a, and this long isoform was abolished by a mutation in the exon 0 start codon. Moreover, the mAno1Ex0-specific N-terminal sequence was immunohistochemically detected in epididymis but not in salivary gland. Our data suggest that mAno1 expression is regulated via alternative promoters, and its transcriptional variation results in variation of the N-terminal sequence of the Ano1 protein due to the alternative translation initiation sites. These tissue-specific variations might contribute to the regulation of mAno1 expression and activity according to the physiological function of each tissue.

C.1289G>A (p.Arg430His) variant in the epsilon isoform of the GFAP gene in a patient with adult onset Alexander disease

Alexander disease (AD) is a rare form of leukodystrophy caused by pathogenic variants in the GFAP gene. In young children the condition is fatal, while adults have variable neurological symptoms and prognosis. On magnetic resonance imaging, a pattern of atrophy of the medulla oblongata and cervical spinal cord with a ‘tadpole’ appearance is highly suggestive of adult-onset Alexander disease (AOAD). GFAP gene sequencing is used to confirm the diagnosis. Pre-mRNA of this gene undergoes alternative splicing resulting in formation of at least 8 different protein isoforms. Most patients with AD described to date have a pathogenic variant in the coding sequence of the main and the most abundant gene isoform, the GFAPα. Recently, two half-siblings with neurological symptoms and radiological signs of AOAD were reported and were not found to have any pathogenic variants in the GFAPα gene while further genetic testing by next generation sequencing revealed a c.1289G>A (p.Arg430His) variant in the alternative exon 7A of the GFAPε isoform.Here we present a case of another patient with symptoms and brain MRI pattern suggestive of AOAD. Similarly to the previously described patients, this patient did not have any pathogenic variants in the main gene isoform and had the same c.1289G>A (p.Arg430His) variant in the GFAPε. This report contributes to evidence of pathogenicity of the c.1289G>A (p.Arg430His) variant in the GFAPε.

Abstract 2481: Loss of FUBP1 impairs terminal neuronal differentiation and predisposes neural progenitors for transformation

Abstract Loss of terminal differentiation capacity through genetic mutations is a selected genetic event in tumorigenesis. 1p19q co-deletion associated recurrent mutations of far upstream element-binding protein 1 (FUBP1) have been reported from genomic analysis of low- grade oligodendroglioma. It is frequently overexpressed in many human cancers and strongly correlated with disease progression. However, left unanswered is how FUBP1 serves uniquely as a tumor suppressor in the central nervous system. Here we show that expression of FUBP1 is dynamically regulated during neurogenesis, marking specific stages of neuronal differentiation. Loss of FUBP1 in neural stem/progenitor cells (NPC) increased the number of cells fail to terminally differentiate. Knockdown of FUBP1 further blocks differentiation and promotes tumorigenesis collaboratively with the expression of neomorphic isocitrate dehydrorgenase 1 mutant IDH1R132H. Mechanistically FUBP1 is necessary for mini exon 8a splicing of neurospecific isoform of histone demethylase LSD1 (nLSD1). It binds to intron 8 of LSD1 together with a neuron-specific splicing complex containing NOVA1 and 2 and works synergistically with SRRM4 for the inclusion of mini exon 8a. The expression level of nLSD1 is decreased upon loss of FUBP1 in neural progenitors, impairing the terminal neuronal differentiation and maturation. Reinforcing nLSD1 expression in FUBP1-downregulated NPC restores terminal differentiation, establishing nLSD1 as an obligatory effector of FUBP1-dependent neuronal differentiation. Together, these findings establish a direct role for FUBP1 in neuronal differentiation and also uncover the mechanism for its tumor suppressor function in the nervous system. Citation Format: Inah Hwang, Dongqing Cao, Do-Yeon Kim, Tuo Zhang, Jian Hu, Yu Yao, Jihye Paik. Loss of FUBP1 impairs terminal neuronal differentiation and predisposes neural progenitors for transformation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2481.