Investigation of the molecular causes underlying physical abnormalities in Diamond‐Blackfan anemia patients with RPL5 haploinsufficiency

Diamond-Blackfan anemia (DBA) is a genetic disorder caused by mutations in genes encoding ribosomal proteins and characterized by erythroid aplasia and various physical abnormalities. Although accumulating evidence suggests that defective ribosome biogenesis leads to p53-mediated apoptosis in erythroid progenitor cells, little is known regarding the underlying causes of the physical abnormalities. In this study, we established induced pluripotent stem cells from a DBA patient with RPL5 haploinsufficiency. These cells retained the ability to differentiate into osteoblasts and chondrocytes. However, RPL5 haploinsufficiency impaired the production of mucins and increased apoptosis in differentiated chondrocytes. Increased expression of the pro-apoptotic genes BAX and CASP9 further indicated that RPL5 haploinsufficiency triggered p53-mediated apoptosis in chondrocytes. MDM2, the primary negative regulator of p53, plays a crucial role in erythroid aplasia in DBA patient. We found the phosphorylation level of MDM2 was significantly decreased in RPL5 haploinsufficient chondrocytes. In stark contrast, we found no evidence that RPL5 haploinsufficiency impaired osteogenesis. Collectively, our data support a model in which RPL5 haploinsufficiency specifically induces p53-mediated apoptosis in chondrocytes through MDM2 inhibition, which leads to physical abnormalities in DBA patients.

This is an Accepted Manuscript of an article published by Wiley.
This is the peer reviewed version of the following article: [Fukui, Y, Hayano, S, Kawanabe, N, Wang, Z, Shimada, A, Saito, MK, et al. Investigation of the molecular causes underlying physical abnormalities in Diamond-Blackfan anemia patients with RPL5 haploinsufficiency. Pathology International. 2021; 1-11. https://doi.org/10.1111/pin.13168], which has been published in final form at [https://doi.org/10.1111/pin.13168]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-ArchivedVersions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wileyor by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked toWiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof bythird parties from platforms, services and websites other than Wiley Online Library must be prohibited.