Mutations in NIPBL are the major cause of Cornelia de Lange Syndrome (CdLS). NIPBL is the cohesin-loading factor and has recently been associated with the BET (bromodomains and extra-terminal (ET) domain) proteins BRD2 and BRD4. Related to this, a CdLS-like phenotype has been described associated to BRD4 mutations. Here, we show direct interaction of NIPBL with different BET members in yeast, and selective interaction with BRD4 in cells, being the ET domain involved in the interaction. To understand the relationship between NIPBL and BET proteins, we have performed RNA-Seq expression analysis following depletion of the different proteins. Results indicate that genes regulated by NIPBL largely overlap with those regulated by BRD4 but not with those regulated by BRD2. ChIP-Seq analysis indicates preferential NIPBL occupancy at promoters, and knockdown experiments show mutual stabilization of NIPBL and BRD4 on co-regulated promoters. Moreover, human fibroblasts from CdLS probands with mutations in NIPBL show reduced BRD4 at co-occupied promoters. Functional analysis in vivo, using mutants of Drosophila melanogaster , confirmed the genetic interaction between Nipped-B and fs(1)h , the orthologs of human NIPBL and BRD4 , respectively. Thus, we provide evidence for NIPBL and BRD4 cooperation in transcriptional regulation, which should contribute to explain the recently observed CdLS-like phenotype associated with BRD4 mutations.

In recent years, many genes have been associated with chromatinopathies classified as “Cornelia de Lange Syndrome‐like.” It is known that the phenotype of these patients becomes less recognizable, overlapping to features characteristic of other syndromes caused by genetic variants affecting different regulators of chromatin structure and function. Therefore, Cornelia de Lange syndrome diagnosis might be arduous due to the seldom discordance between unexpected molecular diagnosis and clinical evaluation. Here, we review the molecular features of Cornelia de Lange syndrome, supporting the hypothesis that “CdLS‐like syndromes” are part of a larger “rare disease family” sharing multiple clinical features and common disrupted molecular pathways.

KMT2A (Lysine methyltransferase 2A) is a member of the epigenetic machinery, encoding a lysine methyltransferase responsible for the transcriptional activation through lysine 4 of histone 3 (H3K4) methylation. KMT2A has a crucial role in gene expression, thus it is associated to pathological conditions when found mutated. KMT2A germinal mutations are associated to Wiedemann–Steiner syndrome and also in patients with initial clinical diagnosis of several other chromatinopathies (i.e., Coffin–Siris syndromes, Kabuki syndrome, Cornelia De Lange syndrome, Rubinstein–Taybi syndrome), sharing an overlapping phenotype. On the other hand, KMT2A somatic mutations have been reported in several tumors, mainly blood malignancies. Due to its evolutionary conservation, the role of KMT2A in embryonic development, hematopoiesis and neurodevelopment has been explored in different animal models, and in recent decades, epigenetic treatments for disorders linked to KMT2A dysfunction have been extensively investigated. To note, pharmaceutical compounds acting on tumors characterized by KMT2A mutations have been formulated, and even nutritional interventions for chromatinopathies have become the object of study due to the role of microbiota in epigenetic regulation.

Cornelia de Lange Syndrome (CdLS) is a choesinopathy: a severe genetic disorder caused by mutations in the cohesin complex genes. The phenotype is characterized by typical facial dysmorphism, growth impairment and multiorgan abnormalities including brain alterations. Wnt pathway is known to play a fundamental role in central nervous system development and it has been shown that Wnt pathway is disrupted in CdLS animal models and patients cells. In this review we investigate the possible link between Wnt pathway disruption and brain abnormalities in Cornelia de Lange Syndrome as such molecular impairment could lead to an abnormal embryonic development resulting in brain abnormalities (i.e. microcephaly, cerebellar hypoplasia, abnormal cortical development) in patients with Cornelia de Lange Syndrome.