l-leucine partially rescues translational and developmental defects associated with zebrafish models of Cornelia de Lange syndrome

Abstract

Cohesinopathies are human genetic disorders that include Cornelia de Lange syndrome (CdLS) and Roberts syndrome (RBS) and are characterized by defects in limb and craniofacial development as well as mental retardation. The developmental phenotypes of CdLS and other cohesinopathies suggest that mutations in the structure and regulation of the cohesin complex during embryogenesis interfere with gene regulation. In a previous project, we showed that RBS was associated with highly fragmented nucleoli and defects in both ribosome biogenesis and protein translation. l-leucine stimulation of the mTOR pathway partially rescued translation in human RBS cells and development in zebrafish models of RBS. In this study, we investigate protein translation in zebrafish models of CdLS. Our results show that phosphorylation of RPS6 as well as 4E-binding protein 1 (4EBP1) was reduced in nipbla/b, rad21 and smc3-morphant embryos, a pattern indicating reduced translation. Moreover, protein biosynthesis and rRNA production were decreased in the cohesin morphant embryo cells. l-leucine partly rescued protein synthesis and rRNA production in the cohesin morphants and partially restored phosphorylation of RPS6 and 4EBP1. Concomitantly, l-leucine treatment partially improved cohesinopathy embryo development including the formation of craniofacial cartilage. Interestingly, we observed that alpha-ketoisocaproate (α-KIC), which is a keto derivative of leucine, also partially rescued the development of rad21 and nipbla/b morphants by boosting mTOR-dependent translation. In summary, our results suggest that cohesinopathies are caused in part by defective protein synthesis, and stimulation of the mTOR pathway through l-leucine or its metabolite α-KIC can partially rescue development in zebrafish models for CdLS.

Requirement of Neuronal Ribosome Synthesis for Growth and Maintenance of the Dendritic Tree

“…reported in non-neuronal cell culture models of these conditions (71,72). Therefore, the pathological sequel triggered by neuronal ribosome deficiency may underlie the neurological phenotype not only in Rett syndrome but also in cohesinopathies.…”

“…Reduced brain growth and mental retardation are also found in Roberts and Cornelia DeLange syndromes that are caused by deficits in chromatin structure proteins that regulate sister chromatid cohesion (18). As in the case of MeCP2 deficiency, these mutations are proposed to disrupt transcription, including rRNA production (71,72). Indeed, ribosomal deficits were FIGURE 9.…”

Methionine Regulates mTORC1 via the T1R1/T1R3-PLCβ-Ca2+-ERK1/2 Signal Transduction Process in C2C12 Cells

“…SLC7A5/SLC3A2 is a bidirectional transporter that regulates the simultaneous efflux of l -glutamine out of cells and the transport of l -leucine/EAA into cells, and this exchange is rate-limiting for the activation of mTORC1 by essential AAs and growth factors [10]. l -leucine also improves ribosomal function through mTORC1 signaling to promote cell division and enhance animal development [33]. However, the molecular mechanism of other AAs involved in regulating mTOR signal transduction remains unclear.…”

How many roads lead to cohesinopathies?

“…Translational impairment also appears to play a role in CdLS phenotypes (Xu et al, ; Zakari et al, ). Evaluation of the rad21, smc3 , and nipbla/b morphants and CdLS patient cells exhibits reduced phosphorylation of the translational markers RPS6 and 4EBP1, consistent with reduced translation.…”