Spotting a unicorn: spatial transcriptome analysis of the eyelid reveals gene regulatory networks enriched in Moll glands.

Moll glands, found in the margin of the eyelid next to the base of the eyelashes, are likely to play an important role in maintaining the tear film and therefore in securing adequate visual function. However, information about their secretion and its regulation is extremely scarce. Here, we subjected spatial transcriptome data of the human eyelid to bioinformatics workflows incorporating machine learning to shed light on the Moll-specific transcriptional program. We identified Moll-specific genes such as HPD, CYP4Z1, PIP, GLYATL2, or SCGB2A2, which delineate a transcriptional core, i.e. not shared with other eyelid elements. Gene ontology enrichment analyses further depicted the biological functions of the Moll gland transcriptional programs, which include tyrosine metabolism and biosynthesis, extracellular exosome, small molecule metabolism, and erythrose 4-phosphate/phosphoenolpyruvate-family amino acid metabolism. Expression of GLYATL2 and HPD, identified as a specific and sensitive transcripts in the Moll gland transcriptome, was confirmed by immunofluorescence in the eyelid of four different patients, thus supporting the validity of our approach. Collectively, these results indicate that Moll-associated gene sets exhibit distinct but complementary functional programs, reflecting the gland's specialized metabolic capacity and secretory function within the eyelid tissue microenvironment. Our study provides the first in-depth analysis of the human Moll gland transcriptional landscape and identifies novel targets for regulating Moll gland homeostasis in health and disease.