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Dlx5 and Dlx6 encode distal-less homeodomain transcription factors that are present in the genome as a linked pair at a single locus. Dlx5 and Dlx6 have redundant roles in craniofacial, skeletal, and uterine development. Previously, we performed a transcriptome comparison for anti-Müllerian hormone (AMH)-induced genes expressed in the Müllerian duct mesenchyme of male and female mouse embryos. In that study, we found that Dlx5 transcripts were nearly seven-fold higher in males compared to females and Dlx6 transcripts were found only in males, suggesting they may be AMH-induced genes. Therefore, we investigated the role of Dlx5 and Dlx6 during AMH-induced Müllerian duct regression. We found that Dlx5 was detected in the male Müllerian duct mesenchyme from E14.5 to E16.5. In contrast, in female embryos Dlx5 was detected in the Müllerian duct epithelium. Dlx6 expression in Müllerian duct mesenchyme was restricted to males. Dlx6 expression was not detected in female Müllerian duct mesenchyme or epithelium. Genetic experiments showed that AMH signaling is necessary for Dlx5 and Dlx6 expression. Müllerian duct regression was variable in Dlx5 homozygous mutant males at E16.5, ranging from regression like controls to a block in Müllerian duct regression. In E16.5 Dlx6 homozygous mutants, Müllerian duct tissue persisted primarily in the region adjacent to the testes. In Dlx5-6 double homozygous mutant males Müllerian duct regression was also found to be incomplete but more severe than either single mutant. These studies suggest that Dlx5 and Dlx6 act redundantly to mediate AMH-induced Müllerian duct regression during male differentiation.

Brice Bellessort,1 Anne Bachelot,1,2 Virginie Grouthier,2 Camille De Lombares,1 Nicolas Narboux-Neme,1 Paolo Garagnani,3,4 Chiara Pirazzini,3,4 Simonetta Astigiano,5 Luca Mastracci,6,7 Anastasia Fontaine,1 Gladys Alfama,1 Evelyne Duvernois-Berthet,1 Giovanni Levi1 1Evolution of Endocrine Regulations, Department AVIV, National Museum of Natural History, Paris, France; 2AP-HP, Department of Endocrinology and Reproductive Medicine, Reference Center for Rare Endocrine Diseases, Pitié-Salpêtrière Hospital, UPMC, Paris, France; 3Department of Experimental, Diagnostic and Specialty Medicine, Alma Mater Studiorum, University of Bologna, Bologna, Italy; 4Interdepartmental Center “L. Galvani”, University of Bologna, Bologna, Italy; 5Department of Integrated Oncological Therapies, San Martino Hospital, Genova, Italy; 6Department of Experimental Medicine and Center of Excellence for Biomedical Research, University of Genoa, Genova, Italy; 7Division of Anatomic Pathology, Department of Surgical Science and Integrated Diagnostics, University of Genoa, Genova, Italy Background: It has been repetitively shown that the transcription factors DLX5 and DLX6 are drastically downregulated in endometriotic lesions when compared with eutopic endometrium. These findings suggest that regulatory cascades involving DLX5/6 might be at the origin of endometriosis symptoms such as chronic pelvic pain (CPP). We have shown that inactivation of Dlx5 and Dlx5/6 in the mouse uterus results in an endometrial phenotype reminiscent of endometriosis. Methods: We focused on genes that present a similar deregulation in endometriosis and in Dlx5/6-null mice in search of new endometriosis targets. Results: We confirmed a strong reduction of DLX5 expression in endometriosis implants. We identified a signature of 30 genes similarly deregulated in human endometriosis implants and in Dlx5/6-null mouse uteri, reinforcing the notion that the downregulation of Dlx5/6 is an early event in the progress of endometriosis. CACNA2D3, a component of the α2δ family of voltage-dependent calcium channel complex, was strongly overexpressed both in mutant mouse uteri and in endometriosis implants, were also CACNA2D1 and CACNA2D2, other members of the α2δ family involved in nociception, are upregulated. Conclusion: Comparative analysis of gene expression signatures from endometriosis and mouse models showed that calcium channel subunits α2δ involved in nociception can be targets for the treatment of endometriosis-associated pain. CACNA2D3 has been associated with pain sensitization and heat nociception in animal models. In patients, CACNA2D3 variants were associated with reduced sensitivity to acute noxious stimuli. As α2δs were targets of gabapentinoid analgesics, the results suggested the use of these drugs for the treatment of endometriosis-associated pain. Indeed, recent small-scale clinical studies have shown that gabapentin could be effective in women with CPP. The findings of this study reinforce the need for a large definitive trial. Keywords: endometriosis, gabapentin, CACNA2D3, Dlx5, pain