De novo loss-of-function variant in PTDSS1 is associated with developmental delay

Glycerophospholipids: Roles in Cell Trafficking and Associated Inborn Errors

Glycerophospholipids (GPLs) are the main lipid components of cellular membranes. They are implicated in membrane structure, vesicle trafficking, neurotransmission, and cell signalling. GPL molecules are amphiphilic, organized around the three carbons of glycerol. Positions sn-1 and sn-2 are each esterified to a fatty acid (FA). At position sn-3, a phosphate group is linked, which in turn can bind a polar head group, the most prevalent classes being phosphatidic acid (PA, phosphate alone as head group), phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), and cardiolipin (CL). Pathways of GPL biosynthesis span several cell compartments (endoplasmic reticulum (ER), Golgi mitochondria). Particularly important are mitochondria-associated membranes (MAMs), where the ER and mitochondrial outer membrane are in proximity. After synthesis, GPLs continuously undergo remodelling by FA hydrolysis and re-esterification. Esterification with different FAs alters membrane properties. Many steps in GPL synthesis and remodelling can be mediated by more than one enzyme, suggesting complexity that requires further exploration. The 38 known GPL-related inborn errors are clinically diverse. 23 (61%) have neurologic features, sometimes progressive and severe, particularly developmental delay/encephalopathy in 16 (42%) and spastic paraplegia in 12 (32%). Photoreceptor/neuroretinal disease occurs in 14 (37%). Three present skeletal dysplasias (8%). Most GPL inborn errors have been diagnosed by broad molecular testing. Lipidomics holds promise for diagnostic testing and for the discovery of functionally relevant metabolite profiles for monitoring natural history and treatment response.

Microglial Dysfunction in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a highly heterogeneous neurodevelopmental disorder with onset in childhood. The molecular mechanisms underlying ASD have not yet been elucidated completely. Evidence has emerged to support a link between microglial dysfunction and the etiology of ASD. This review summarizes current research on microglial dysfunction in neuroinflammation and synaptic pruning, which are associated with altered transcriptomes and autophagy in ASD. Dysbiosis of gut microbiota in ASD and its correlation with microglial dysfunction are also addressed.

Biochemistry and Diseases Related to the Interconversion of Phosphatidylcholine, Phosphatidylethanolamine, and Phosphatidylserine

Phospholipids are crucial structural components of cells. Phosphatidylcholine and phosphatidylethanolamine (both synthesized via the Kennedy pathway) and phosphatidylserine undergo interconversion. The dysregulation of this process is implicated in various diseases. This paper discusses the role of enzymes involved in the interconversion of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine, specifically phosphatidylethanolamine N-methyltransferase (PEMT), phosphatidylserine synthases (PTDSS1 and PTDSS2), and phosphatidylserine decarboxylase (PISD), with a focus on their biochemical properties. Additionally, we describe the effects of the deregulation of these enzymes and their roles in both oncological and non-oncological diseases, including nonalcoholic fatty liver disease (NAFLD), Alzheimer's disease, obesity, insulin resistance, and type II diabetes. Current knowledge on inhibitors of these enzymes as potential therapeutic agents is also reviewed, although in most cases, inhibitors are yet to be developed. The final section of this article presents a bioinformatic analysis using the GEPIA portal to explore the significance of these enzymes in cancer processes.

Loss of function of phosphatidylserine synthase causes muscle atrophy in Drosophila

Maintenance of appropriate muscle mass is crucial for physical activity and metabolism. Aging and various pathological conditions can cause sarcopenia, a condition characterized by muscle mass decline. Although sarcopenia has been actively studied, the mechanisms underlying muscle atrophy are not well understood. Thus, we aimed to investigate the role of Phosphatidylserine synthase (Pss) in muscle development and homeostasis in Drosophila. The results showed that muscle-specific Pss knockdown decreased exercise capacity and produced sarcopenic phenotypes. In addition, it increased the apoptosis rate because of the elevated reactive oxygen species production resulting from mitochondrial dysfunction. Moreover, the autophagy rate increased due to increased FoxO activity caused by reduced Akt activity. Collectively, these findings demonstrate that enhanced apoptosis and autophagy rates resulting from muscle-specific Pss knockdown jointly contribute to sarcopenia development, highlighting the key role of the PSS pathway in muscle health.