RESUMEN
Evolution has long been considered to be a conservative process in which new genes arise from pre-existing genes through gene duplication, domain shuffling, horizontal transfer, overprinting, retrotransposition, etc. However, this view is changing as new genes originating from non-genic sequences are discovered in different organisms. Still, rather limited functional information is available. Here, we have identified TWISTED1 (TWT1), a possible de novo-originated protein-coding gene that modifies microtubule arrangement and causes helicoidal growth in Arabidopsis thaliana when its expression is increased. Interestingly, even though TWT1 is a likely recent gene, the lack of TWT1 function affects A. thaliana development. TWT1 seems to have originated from a non-genic sequence. If so, it would be one of the few examples to date of how during evolution de novo genes are integrated into developmental cellular and organismal processes.
RESUMEN
BACKGROUND: Trisomy 13 or Patau syndrome has a prevalence of 1:10,000-20,000 and is characterized by microcephaly, microphthalmia, polydactyly, as well as other dysmorphic features and malformations, with a patient survival of 13% in the first year. Trisomy 13 presents either as a free chromosome 13 trisomy or associated with a chromosomal Robertsonian translocation, as partial trisomy affecting proximal or distal 13q regions, and also as a mosaic. Mosaic trisomy 13 shows a highly variable phenotype, displaying from mild to severe affectations. We present a 12-year-old Mexican female patient with intellectual disability, dysmorphic features, polymenorrhea, and long survival, whose initial cytogenetic study referred to a small supernumerary marker chromosome. METHODS: GTG banding karyotype, high-resolution chromosomal microarray, and fluorescent in situ hybridization analyses were performed in peripheral blood cells. RESULTS: Our analyses demonstrated a de novo mosaicism in our patient, constituted by proximal trisomy 13q10-q14.3 (82%) and free trisomy 13 (18%) cell lines. Her final chromosomal complement is mos 47,XX,+del(13)(q14.3)[25]/47,XX,+13[7].ish del(13)(RB1+)[17]/13q14(RB1x3)[2].arr[GRCh37] 13q11q14.3(19436286_51726415)x3,13q11q34(19436286_115107733)x2-3 dn. CONCLUSIONS: The wide spectrum of clinical manifestations observed in our patient mainly results from the proximal trisomy 13q, and her phenotype is modified by the presence of a free trisomy 13 cell line. We propose that her mosaicism probably derived from a trisomic zygote that underwent a failed trisomic rescue associated with chromothripsis, originating the cell line with partial 13q proximal trisomy, whose selective advantage could explain the long survival of our patient.
