Molecular characterization of X-linked cognitive disorders in which language impairment is a prominent symptom decisively contributes to a better understanding of the genetic programme involved in the development of the language organ. Proteins encoded by genes mutated in these disorders are structurally and functionally diverse: (i) helicases, (ii) homebox proteins, (iii) transcriptional regulators, (iv) translational regulators, (v) posttranslational regulators, and (vi) phosphoproteins. These proteins ultimately modulateneural development and function, as far as they seem to be involved in the regulation of (i) neural migration, (ii) neural identity, (iii) axonal growth, (iv) dendritic proliferation, (v) synaptogenesis, (vi) myelinization, (vii) neural plasticity, (viii) long-term potentiation and (ix) neural survival, but also in the modulation of basic cellular processes, like (x) chromosome segregation. Though these genes clearly make up the genetic programmes responsible for the emergence of different cognitive modules, they should be taken necessarily into account for an accurate molecular characterization of the language organ, since it is only programmes, but not genes, that should be properly regarded as idiosyncratic (i.e. most genes cannot reasonably be characterized as “linguistic”, unlike the programme itself related to the language organ).

Key words: language, cognition, chromosome X, molecular biology.