All living organisms possess mechanisms to protect themselves from their environment. The cuticle (including epicuticle) and the surface coat are physical barriers that protect nematodes from their external environment. The protein composition of the cuticle is well characterized; however, the lipid composition of the epicuticle, an important layer of the surface barrier, lacks characterization. To understand how the epicuticle of C. elegans confers physical protection, we are studying its lipid composition. We previously showed that the protective surface barrier is affected by DBL-1/TGF-? (Transforming Growth Factor-?) signaling in a dose-dependent manner. Previously published microarray analyses indicate that DBL-1 regulates lipid metabolism genes. We developed a protocol to enrich surface lipids from the epicuticle from the rest of the lipid composition of the worm (i.e., internal lipids). To determine if DBL-1 affects the general lipid composition of surface and internal lipids, we used thin layer chromatography. We observed common lipid classes (e.g., phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidic acid, and triacylglycerols) in both surface and internal lipid extractions regardless of DBL-1 expression. We also observed a decrease in the internal triacylglycerol levels between wild-type and
dbl-1(
nk3) animals, supporting previously published data. Next, to determine if the DBL-1 pathway affects the fatty acid composition of surface and inside lipids, we used gas chromatography-mass spectrometry to identify, quantitate, and compare surface lipids to internal lipids of wild-type and
dbl-1 knockout populations. We determined that relative levels of specific surface-enriched lipids are reduced by loss of DBL-1. We also observed a difference in the acyl moieties of the inside lipids of
dbl-1 knockout populations compared with wild-type populations. We conclude that while the same lipid classes are represented in both wild-type and
dbl-1(
nk3) populations, the composition of the lipid classes is different. Lastly, to identify lipid metabolism genes regulated by DBL-1, we performed RNA-seq of wild-type and
dbl-1(
nk3) at 48 hours after L4. Our preliminary results validate and expand on the DBL-1-regulated lipid metabolism genes previously identified by microarray analyses. This study 1) identifies the specific lipid composition of the C. elegans surface barrier of both wild-type and
dbl-1 mutant animals and 2) will help characterize underlying molecular mechanisms for synthesis of surface barrier lipids regulated by DBL-1.