“Molecular mechanisms mediating negative emotion and contributing to major depression remain elusive: here, (the authors) present evidence implicating fibroblast growth factor 9 (FGF9) as a key mediator. …..whole-transcriptome studies of postmortem human tissue were used to demonstrate that FGF9 is elevated in depression. Reverse translation animal studies demonstrate that both endogenous and exogenous FGF9 promote anxiety- and depression-like behavior. Conversely, localized blockade of endogenous FGF9 expression decreases anxiety behavior. …This paper is the first description of hippocampal FGF9 function and the first evidence implicating FGF9 in negative affect. Thus, FGF9 represents a novel target for treating affective disorders.” They suggest that FGF2 and FGF9 work in functional opposition and hypothesize that the balance between FGF factors may prove critical for optimal regulation of mood.

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Aurbach EL, Inui EG, Turner CA, Hagenauer MH, Prater KE, Li JZ, Absher D, Shah N, Blandino P Jr, Bunney WE, Myers RM, Barchas JD, Schatzberg AF, Watson SJ Jr, Akil H: Fibroblast growth factor 9 is a novel modulator of negative affect. Proc. Natl. Acad. Sci. [Epub ahead of print, Sept.8, 2015] pii: 201510456.

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http://www.ncbi.nlm.nih.gov/pubmed/26351673