In Down syndrome (Trisomy 21), the most common chromosomal condition leading to intellectual disability worldwide, the newly described BAF complex-associated factor BRWD1 (encoded on chromosome 21) was found to be significantly upregulated in patient-derived neurons and in brain tissues from a mouse model for Down syndrome (Ts65Dn)150,151 (Antonarakis et al. The gene discussed is BRWD1; the disease is Down syndrome.