Obesity is a global health threat, which continues to rise in prevalence worldwide, driving increases in related chronic diseases such as type 2 diabetes and cardiovascular conditions. While the sheer scale of the crisis affects over a billion people worldwide, the challenge is compounded for a distinct population: patients with genetically inherent obesity. Gene therapy targeting adipose tissue offers promise for treating obesity, but it requires development of tissue-targeting methods to minimize off-target effects and ensure safety. Our study presents two strategies to restrict transgene expression specifically to adipocytes: engineered adipose-specific promoters and optogenetic regulation. We designed truncated promoter fragments from murine Ucp1, Adipoq, and Fabp4 genes and evaluated their activity during 3T3-L1 preadipocyte differentiation. While all adipocyte-specific promoters exhibited substantially lower activity than the constitutive Cytomegalovirus promoter (10- to 100-fold reduction), they displayed distinct temporal activation patterns: Ucp1 peaked during active differentiation, whereas Adipoq was predominantly active in mature adipocytes. In vivo validation using AAV6/8 vectors confirmed adipose expression of the fluorescent reporter Katushka2S under the Ucp1 promoter in murine interscapular fat. Bioinformatic analysis (MAST/MCAST) of six adipocyte-enriched genes (Fabp4, Adipoq, Ucp1, Lep, Cidec, Sfrp5) identified high-density transcription factor binding site clusters that can be used for the development of new promoters for adipose-specific expression. Furthermore, we implemented the iLight optogenetic system to achieve light-dependent reassembly of split FOXP4 and PRDM16 transcription factors, demonstrating tunable Ucp1 activation with minimal basal expression. These strategies—development of synthetic adipose-specific mini-promoters and light-inducible regulation—may serve as a basis for developing precision metabolic medicine as these approaches allow spatiotemporal control of transgene expression.

Lipid nanoparticles (LNPs) are an effective platform for delivering therapeutic payloads, but their use for targeting specific cell populations in vivo is limited by a lack of specificity. To address this issue, we developed an innovative approach for creating targeted LNPs based on the post-insertion of protein–lipid conjugates. By expanding the genetic code, a single p-azido-L-phenylalanine residue was specifically incorporated into a DARPin against murine CD8, enabling copper-free click-chemistry with dibenzocyclooctyne (DBCO) to functionalize the particle surface with DARPin conjugates. DARPin-LNP characterization demonstrated preservation of particle size and acquisition of a characteristic negative charge after DARPin insertion, confirming successful post-insertion. In vitro experiments using primary murine splenic T-cells showed that targeted LNPs selectively transfected CD8⁺ T-lymphocytes. These data indicate that the developed platform enables selective in vitro delivery of nucleic acids to cytotoxic lymphocytes, highlighting its potential relevance for designing safer immunotherapeutic strategies.

Chronic inflammation and subfertility converge on a number of ligand-dependent transcription factors induced by chemically heterogeneous environmental exposures. Foremost among them is the aryl hydrocarbon receptor (AhR), of the basic helix-loop-helix (bHLH)–PER-ARNT-SIM (PAS) superfamily. Identified first as the receptor for dioxins and long regarded as a mediator of xenobiotic toxicity, AhR is now established as a regulator of physiological homeostasis, responding to microbial, dietary, phytochemical substances and endogenously generated metabolites. In this review, we examine AhR ligands and the transcriptional programmes they elicit, organising the evidence around one distinction: whether a ligand is a substrate for the cytochrome P450 enzymes it induces, and therefore self-limiting, or whether it persists and converts a single exposure into a chronic stimulus. We follow the receptor through the gastrointestinal tract, skin and adipose tissue; through the eye, where biallelic loss-of-function genetic variants cause foveal hypoplasia and retinitis pigmentosa and through the reproductive axis, where AhR sets ovarian aromatase expression, follicular recruitment, spermatogenesis and trophoblast invasion. Spanning the good, the bad, the ugly and the blind, we argue that therapeutic progress depends not on deciding whether to activate or inhibit AhR, but on confining modulation to a defined tissue, ligand residence time and transcriptional output.