Novel fatty acid desaturase 3 (FADS3) transcripts generated by alternative splicing

Abstract

Fatty acid desaturase 1 and 2 (FADS1 and FADS2) code for the key desaturase enzymes involved in the biosynthesis of long chain polyunsaturated fatty acids in mammals. FADS3 shares close sequence homology to FADS1 and FADS2 but the function of its gene product remains unknown. Alternative transcripts (AT) generated by alternative splicing (AS) are increasingly recognized as an important mechanism enabling a single gene to code for multiple gene products. We report the first AT of a FADS gene, FADS3, generated by AS. Aided by ORF Finder, we identified putative coding regions of eight AT for FADS3 with 1.34 kb (classical splicing), 1.14 (AT1), 0.77 (AT2), 1.25 (AT3), 0.51 (AT4), 0.74 (AT6), and 1.11 (AT7). In addition we identified a 0.51 kb length transcript (AT5) that has a termination codon within intron 8-9. The expression of each AT was analyzed in baboon neonate tissues and in differentiated and undifferentiated human SK-N-SH neuroblastoma cells. FADS3 AT are expressed in 12 neonate baboon tissues and showed reciprocal increases and decreases in expression changes in response to human neuronal cell differentiation. FADS3 AT, conserved in primates and under metabolic control in human cells, are a putative mediator of LCPUFA biosynthesis and/or regulation.

The polypyrimidine tract binding protein regulates desaturase alternative splicing and PUFA composition

“…The alternative transcripts (AT) and in vivo expression patterns of FADS2 and FADS3 splice variants have been described in detail previously ( 12,14 ). Approximately 30 nt regions fl anking splice mRNA levels ( Fig.…”

“…Animal protocols were approved by the SFBR and Cornell University Institutional Animal Care and Use Committee (IACUC, protocol #02-105.) Baboon tissue and cell culture RNA was extracted, RNA integrity assessed, cDNA prepared, and semiquantitative RT-PCR carried out as described previously ( 14 ). PCR primers designed for FADS splice variants (Integrated DNA Technologies, sequences available upon request) were validated by cloning and sequencing PCR products.…”

Trans-vaccenate is Δ13-desaturated by FADS3 in rodents

“…The pure trans 11, trans 13-18:2 was obtained from Larodan (Malmö, Sweden). [1][2][3][4][5][6][7][8][9][10][11][12][13] C] trans -vaccenic acid (chemical purity 95%, isotopic enrichment 99%) was synthesized by the Commissariat à l'Energie Atomique (CEA, Gif-sur-Yvette, France) according to well-established procedures ( 27,28 ). FA albuminic complexes were prepared as described ( 26 ).…”

“…FADS3 mRNA was shown to be ubiquitously expressed in a large variety of tissues in humans ( 7 ), baboons ( 12 ), and rats ( 11 ), with a specifi c distribution compared with FADS1 and FADS2 mRNAs. In neonate baboon tissues, seven alternative transcripts of FADS3 were described ( 12 ), but when they were cloned and expressed into yeast and mammalian cells, no activity toward a variety of PUFA substrates was detected ( 16 ). Interestingly, the expression of the FADS3 transcripts was upregulated by dietary long-chain PUFAs, whereas FADS1 and FADS2 mRNA levels were decreased ( 17 ).…”

“…Rat hepatocytes were incubated for 24 h with media supplemented with TVA or [1][2][3][4][5][6][7][8][9][10][11][12][13] C]TVA and with a control medium without FA. RA (R t = 27.5 min) produced by ⌬ 9-desaturation of TVA was easily detected (7.6 ± 3.2% of FA, n = 5) in the cells incubated with TVA or 13 C-TVA ( Fig.…”