TMEM68 (transmembrane protein 68) is an endoplasmic reticulum-anchored acyltransferase that functions as a catalytic subunit of an alternative triacylglycerol (TAG) biosynthesis pathway 1. The protein synthesizes TAG from diacylglycerol and membrane phospholipids (particularly phosphatidylcholine and ether-linked phosphatidylcholine), thereby remodeling membrane lipid composition 1. TMEM68 exhibits both monoacylglycerol acyltransferase (MGAT) and diacylglycerol acyltransferase (DGAT) activities 2, operating independently of the canonical DGAT1/2 pathway 3. Mechanistically, TMEM68 is regulated by TMX1 at the endoplasmic reticulum, with loss of TMX1 leading to unconstrained lipid droplet formation 1. The pathway maintains mitochondrial function during extracellular lipid starvation and supports rapid growth when fuel sources are limiting 1. Beyond TAG synthesis, TMEM68 acts as a multifaceted regulator of membrane lipid homeostasis, reducing ether-linked glycerophospholipids and polyunsaturated fatty acids while increasing TAG and lipid droplet storage 3. Clinically, TMEM68 upregulation is associated with breast cancer proliferation and invasion, with higher expression correlating with poorer survival outcomes 4. TMEM68 was identified as a candidate modifier of breast cancer risk in genomic studies 5, and suggestive associations exist with dementia-related proteinopathy 6.