Richieri-Costa-Pereira syndrome is an autosomal-recessive acrofacial dysostosis characterized by mandibular median cleft associated with other craniofacial anomalies and severe limb defects. Learning and language disabilities are also prevalent. We mapped the mutated gene to a 122 kb region at 17q25.3 through identity-by-descent analysis in 17 genealogies. Sequencing strategies identified an expansion of a region with several repeats of 18- or 20-nucleotide motifs in the 50 untranslated region (50 UTR) of EIF4A3, which contained from 14 to 16 repeats in the affected individuals and from 3 to 12 repeats in 520 healthy individuals. A missense substitution of a highly conserved residue likely to affect the interaction of eIF4AIII with the UPF3B subunit of the exon junction complex in trans with an expanded allele was found in an unrelated individual with an atypical presentation, thus expanding mutational mechanisms and phenotypic diversity of RCPS. EIF4A3 transcript abundance was reduced in both white blood cells and mesenchymal cells of RCPSaffected individuals as compared to controls. Notably, targeting the orthologous eif4a3 in zebrafish led to underdevelopment of several craniofacial cartilage and bone structures, in agreement with the craniofacial alterations seen in RCPS. Our data thus suggest that RCPS is caused by mutations in EIF4A3 and show that EIF4A3, a gene involved in RNA metabolism, plays a role in mandible, laryngeal, and limb morphogenesis. ; Fil: Favaro, Francine P. Universidade de Sao Paulo; Brasil ; Fil: Alvizi, Lucas. Universidade de Sao Paulo; Brasil ; Fil: Zechi Ceide, Roseli M. Universidade de Sao Paulo; Brasil ; Fil: Bertola, Debora. Universidade de Sao Paulo; Brasil ; Fil: Felix, Temis M. Universidade Federal do Rio Grande do Sul; Brasil ; Fil: de Souza, Josiane. Centro de Atendimento Integral ao Fissurado La´bio Palatal; Brasil ; Fil: Raskin, Salmo. Pontifícia Universidade Católica do Paraná. Núcleo de Investigação Molecular Avançada. Centro de Ciências Biológicas e da Saúde; Brasil ; Fil: Twigg, Stephen R. F. University of Oxford; Reino Unido ; Fil: Weiner, Andrea Maria Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentina ; Fil: Armas, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentina ; Fil: Margarit, Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentina ; Fil: Calcaterra, Nora Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; Argentina ; Fil: Andersen, Gregers R. University Aarhus; Dinamarca ; Fil: McGowan, Simon J. University of Oxford; Reino Unido ; Fil: Wilkie, Andrew O. M. University of Oxford; Reino Unido ; Fil: Richieri Costa, Antonio. Universidade de Sao Paulo; Brasil ; Fil: de Almeida, Maria L. G. Universidade de Sao Paulo; Brasil ; Fil: Passos Bueno, Maria Rita. Universidade de Sao Paulo; Brasil