PT - JOURNAL ARTICLE AU - Parrini, Elena AU - Mei, Davide AU - Pisanti, Maria Antonietta AU - Catarzi, Serena AU - Pucatti, Daniela AU - Bianchini, Claudia AU - Mascalchi, Mario AU - Bertini, Enrico AU - Morrone, Amelia AU - Cavaliere, Maria Luigia AU - Guerrini, Renzo TI - Familial periventricular nodular heterotopia, epilepsy and Melnick–Needles Syndrome caused by a single <em>FLNA</em> mutation with combined gain-of-function and loss-of-function effects AID - 10.1136/jmedgenet-2014-102959 DP - 2015 Jun 01 TA - Journal of Medical Genetics PG - 405--412 VI - 52 IP - 6 4099 - http://jmg.bmj.com/content/52/6/405.short 4100 - http://jmg.bmj.com/content/52/6/405.full SO - J Med Genet2015 Jun 01; 52 AB - Background Loss-of-function mutations of the FLNA gene cause a neuronal migration disorder defined as X-linked periventricular nodular heterotopia (PNH); gain-of-function mutations are associated with a group of X-linked skeletal dysplasias designed as otopalatodigital (OPD) spectrum. We describe a family in which a woman and her three daughters exhibited a complex phenotype combining PNH, epilepsy and Melnick–Needles syndrome (MNS), a skeletal disorder assigned to the OPD spectrum. All four individuals harboured a novel non-conservative missense mutation in FLNA exon 3. Methods In all affected family members, we performed mutation analysis of the FLNA gene, RT-PCR, ultradeep sequencing analysis in FLNA cDNAs and western blot in lymphocyte cells to further characterise the mutation. We also assessed the effects on RT-PCR products of treatment of patients’ lymphocytes with cycloheximide, a nonsense mediated mRNA decay (NMD) inhibitor. Results We identified a novel c.622G&gt;C change in FLNA exon 3, leading to the substitution of a highly conserved aminoacid (p.Gly208Arg). Gel electrophoresis and ultradeep sequencing revealed the missense mutation as well as retention of intron 3. Cycloheximide treatment demonstrated that the aberrant mRNA transcript-retaining intron 3 is subjected to NMD. Western blot analysis confirmed reduced FLNA levels in lymphocyte cells. Conclusions The novel c.622G&gt;C substitution leads to two aberrant FLNA transcripts, one of which carries the missense mutation, plus a longer transcript resulting from intron 3 retention. We propose that the exceptional co-occurrence of PNH and MNS, two otherwise mutually exclusive allelic phenotypes, is the consequence of a single mutational event resulting in co-occurring gain-of-function and loss-of-function effects.