UGT1A1 Variants c.864+5G>T and c.996+2_996+5del of a Crigler-Najjar Patient Induce Aberrant Splicing in Minigene Assays

A large fraction of DNA variants impairs pre-mRNA splicing in human hereditary disorders. Crigler-Najjar syndrome (CNS) is characterized by a severe unconjugated hyperbilirubinemia caused by variants in the gene. We previously reported one CNS-type II patient with two splice-site variants in trans (...

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Veröffentlicht in:Frontiers in genetics 2020-03, Vol.11, p.169-169
Hauptverfasser: Gailite, Linda, Valenzuela-Palomo, Alberto, Sanoguera-Miralles, Lara, Rots, Dmitrijs, Kreile, Madara, Velasco, Eladio A
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Sprache:eng
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Zusammenfassung:A large fraction of DNA variants impairs pre-mRNA splicing in human hereditary disorders. Crigler-Najjar syndrome (CNS) is characterized by a severe unconjugated hyperbilirubinemia caused by variants in the gene. We previously reported one CNS-type II patient with two splice-site variants in trans (c.864+5G>T and c.996+2_996+5del). According to MaxEntScan, both disrupt their corresponding donor sites (c.864+5G>T: 6.99 → 2.28; c.996+2_996+5del: 5.96 → -11.02), so they were selected for subsequent functional tests. Given the unavailability of patient RNA, we constructed an splicing-reporter minigene with exons 1-4 to characterize the underlying splicing anomaly. The variant c.996+2_996+5del generated two aberrant transcripts, Δ(E2) (exon 2 skipping/64%) and ▼(E2q135) (intron retention of 135-nt/36%), which lead to the loss of 18 conserved amino-acids and the gain of 45 new ones of a critical functional domain, respectively. The c.864+5G>T variant mainly produced the aberrant transcript Δ(E1q141) (141-nt deletion/70.4%) and the full-length isoform (29.6%). Δ(E1q141) would provoke the loss of 47 amino-acids of the N-terminal domain that encodes for substrate specificity. Thus, the three anomalous transcripts are likely to inactivate . Moreover, this patient is also homozygous for the promoter variant A(TA)7TAA that decreases expression by 70%, so the full-length transcript produced by c.864+5G>T would be even more reduced (
ISSN:1664-8021
1664-8021
DOI:10.3389/fgene.2020.00169