title: Novel physiological RECQL4 alternative transcript disclosed by molecular characterisation of Rothmund-Thomson Syndrome sibs with mild phenotype.
abstract: Rothmund-Thomson syndrome is a rare genodermatosis caused by biallelic mutations of the RECQL4 gene and is characterised by poikiloderma, sparse hair, eyelashes and/or eyebrows, small stature, skeletal and dental abnormalities and cancer predisposition. Mutations predicted to result in the loss of RECQL4 protein have been associated with osteosarcoma risk, but mutation(s)-phenotype correlations are better addressed by combined DNA and RNA analyses. We describe two siblings with a mild phenotype, mainly restricted to the skin, who carry the unreported paternal c.2272C>T alteration in exon 14 and the previously reported maternal exon 15 c.2492_2493delAT, both predicted to result in premature termination codons (p.(Arg758*), p.(His831Argfs*52)). However real-time and transcript analysis showed, in the carrier father and affected daughter, increased levels of a novel RECQL4 physiological alternative transcript with partial in-frame skipping of exon 14, generated by increased usage of a weak cryptic splice site. This alternative transcript is expressed in all controls and tested tissues, its upregulation is specific to the paternal c.2272C>T mutation and depends on the abrogation of the binding motifs for SF2 and SRp55 serine/arginine-rich proteins with bypass of the mutation site located in the skipped exon 14 portion. Moreover, in the proband the increased levels of the alternative transcript, likely encoding a protein isoform with residual activity, may compensate for the dearth of the canonical transcript with the c.2492_2493delAT, accounting for the mild clinical phenotype of the siblings. Our results emphasise the value of RNA analysis to better predict the effects of RECQL4 mutations on the clinical phenotype.
authors: Genetica Medica Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milano, Italy.
authors: Elisa Adele
authors: EA
authors: Colombo
authors: Genetica Medica Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milano, Italy.
authors: Laura
authors: L
authors: Fontana
authors: Department of Surgery and Translational Medicine, University of Milan-Bicocca, Monza, Italy.
authors: Gaia
authors: G
authors: Roversi
authors: Genetica Medica Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milano, Italy.
authors: Gloria
authors: G
authors: Negri
authors: Laboratory of Molecular and Cell Biology, Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome, Italy.
authors: Daniele
authors: D
authors: Castiglia
authors: Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome, Italy.
authors: Mauro
authors: M
authors: Paradisi
authors: Laboratory of Molecular and Cell Biology, Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome, Italy.
authors: Giovanna
authors: G
authors: Zambruno
authors: Genetica Medica Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milano, Italy.
authors: Lidia
authors: L
authors: Larizza
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D002460:Cell Line; D002648:Child; D018389:Codon, Nonsense / Q000235:genetics / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D005091:Exons; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D053484:RecQ Helicases / Q000235:genetics* / Q000378:metabolism; D011038:Rothmund-Thomson Syndrome / Q000175:diagnosis / Q000235:genetics*; D017422:Sequence Analysis, DNA; D035781:Siblings; D012867:Skin / Q000378:metabolism
chemical_list: D018389:Codon, Nonsense; D018076:DNA, Complementary; C506731:RECQL4 protein, human; D053484:RecQ Helicases