Deletion of Dock7 Exons 3 and 4 - Results in Reduced Trabecular Microarchitecture and a Decrease in Mineralization

Sep 29, 2026

Dedicator of Cytokinesis 7 (DOCK7) functions as a regulator of skeletal homeostasis, yet prior Dock7 mutant models used only global mutations and did not enable tissue-specific deletion work. Researchers created a Dock7-floxed allele with exons 3–4 flanked by LoxP sites, then globally deleted exons 3–4 to produce Dock7em2/em2 mice. In 21-week-old males and females, trabecular bone volume in distal femur and L5 vertebrae decreased by 30–37%, while cortical thickness stayed unchanged. Dock7em2/em2 bone marrow stromal cells showed reduced mineralization and diminished Bglap expression, indicating impaired osteoblast differentiation. These results establish exons 3–4 as required for normal trabecular bone acquisition and osteoblast function and support Dock7em2/em2 as a valid loss-of-function foundation for future tissue-specific studies.

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Abstract

Introduction

bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.31.696872](https://doi.org/10.64898/2025.12.31.696872); this version posted January 2, 2026. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 1 Deletion of Dock7 Exons 3 and 4 Results in Reduced Trabecular Microarchitecture and a 2 Decrease in Mineralization 3 4 Talia Lizottea , Conner Lajoieb , Sarah Portera , Sydney Langc , Felix A. Vespera , Daniel J. Brooksd , 5 Carlos Gartnere , Matthew S. Alexanderf, Calvin Varye , Mary L. Bouxseinc , Kathleen A. Beckerae 6 7 a Department of Biomedical Sciences, College of Osteopathic Medicine, University of New 8 England, Biddeford, ME 04005, USA 9 b College of Osteopathic Medicine, University of New England, Biddeford, ME 04005, USA 10 c College of Arts and Sciences, University of New England, Biddeford, ME 04005, USA 11 d Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA 12 e Center for Molecular Medicine, MaineHealth Institute for Research, Scarborough, ME 04074, 13 USA 14 f University of Alabama at Birmingham Heersink School of Medicine and Children’s of Alabama, 15 Department of Pediatrics, Division of Neurology, Birmingham, AL, USA 35294 16 Corresponding author: 17 Kathleen Becker, Ph. D. 18 College of Osteopathic Medicine 19 Department of Biomedical Sciences 20 11 Hills Beach Rd 21 Biddeford, ME 04005 22 Tel (207) 602-2824 23 [kbecker3@une.edu](kbecker3@une.edu) 24 25 Keywords: Dock7, osteoblast, bone, trabecular bone, Bglap bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.31.696872](https://doi.org/10.64898/2025.12.31.696872); this version posted January 2, 2026. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC 4.0 International license. 27 Abstract 28 Dedicator of Cytokinesis 7 (DOCK7) has recently emerged as a regulator of skeletal 29 homeostasis, but existing Dock7 mutant models harbor only global mutations and are 30 incompatible with tissue-specific deletion studies. We previously generated a Dock7-floxed 31 allele in which exons 3–4 are flanked by LoxP sites. To validate the utility of this allele for future 32 conditional strategies, we globally deleted exons 3–4 to generate Dock7em2/em2 mice and 33 characterized their skeletal phenotype. Dock7em2/em2 mice exhibited a diluted coat color and 34 white belly spot, consistent with spontaneous Dock7 mutations. Bone microarchitecture was 35 assessed in 21-week-old males and females. Global deletion of Dock7 exons 3–4 resulted in a 36 30–37% reduction in trabecular bone volume in the distal femur and L5 vertebrae. Cortical bone 37 thickness was unchanged in both sexes; however, male Dock7em2/em2 mice displayed reduced 38 total femoral area, whereas females showed increased medullary area. These data suggest 39 altered appositional bone growth with mutation of Dock7. To assess osteoblast function, bone 40 marrow stromal cells (BMSCs) were differentiated in vitro. Dock7em2/em2 BMSCs exhibited 41 reduced mineralization and decreased Bglap expression, indicating attenuated osteoblast 42 differentiation. These findings demonstrate that Dock7 exons 3–4 are required for normal 43 trabecular bone acquisition and osteoblast function. Loss of these exons disrupts DOCK7 44 activity, supporting the Dock7em2/em2 line as a valid loss-of-function model. The Dock7em2/em2 45 mouse provides a foundation for future tissue-specific deletion studies to define the cellular 46 roles of DOCK7 in regulating bone formation and trabecular architecture. 47 bioRxiv preprint doi: [https://doi.org/10.64898/2025.12.31.696

FAQs

What genetic change was introduced to study DOCK7 function?

Exons 3–4 of Dock7 were flanked by LoxP sites in a floxed allele, and then exons 3–4 were globally deleted to generate Dock7em2/em2 mice.

How did the Dock7 exons 3–4 deletion affect bone microarchitecture?

Global deletion of Dock7 exons 3–4 produced a 30–37% reduction in trabecular bone volume in the distal femur and L5 vertebrae, while cortical bone thickness was unchanged.

What evidence shows altered osteoblast function in Dock7em2/em2 mice?

Bone marrow stromal cells differentiated in vitro exhibited reduced mineralization and decreased Bglap expression, indicating attenuated osteoblast differentiation.

Sep 29, 2026

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