Synthesis of mevalonate for the production of non-sterol isoprenoids, which are essential for growth differentiation. Provides spatial information during embryogenesis to guide migrating primordial germ cells (the pole cells) from the ectoderm to the mesoderm. Also required for association of the pole cells with the gonadal mesoderm. (R)-mevalonate + CoA + 2 NADP(+) = (3S)-hydroxy-3-methylglutaryl-CoA + 2 H(+) + 2 NADPH The activity of HMG-CoA-reductase is suppressed by exogenous mevalonate. Metabolic intermediate biosynthesis; (R)-mevalonate biosynthesis; (R)-mevalonate from acetyl-CoA: step 3/3. Highly expressed in embryonic gonadal mesoderm, where expression is initially broad, and then becomes restricted to a segmental pattern at stage 11. Expression is then further restricted to a cluster of cells in each of parasegments 10, 11 and 12, corresponding to the developing gonadal mesoderm. Not expressed in pole cells. Belongs to the HMG-CoA reductase family.