Biology subjects

Wallace, J. M.

Publications and source records attributed to Wallace, J. M..

4 recordsLinked to original sources

bioRxiv2026

Site-, strain- and mutation-specific osteopetrosis phenotypes in mice with Clcn7 variants

Background: Autosomal dominant osteopetrosis type II (ADOII) is a rare bone disorder caused primarily by heterozygous mutations in CLCN7 and characterized by increased bone mass yet fragility and marked phenotypic heterogeneity among affected individuals. The biological factors underlying this variability remain poorly understood. We investigated the effects of age, sex, genetic background, and mutation type on bone phenotypes in murine models of ADOII carrying heterozygous Clcn7 F318L/+ or G213R/+ mutations. Methods: Bone microarchitecture was assessed by micro-computed tomography in vertebrae and femora from female and male mice across multiple ages (12, 24, and 52 weeks) and strain backgrounds (FVB/NJ, C57BL/6, and 129). Vertebral biomechanical properties were estimated by micro-finite element analysis, while femoral mechanical properties were measured using three-point bending. Results: Clcn7 F318L/+ mice exhibited significantly increased trabecular bone compared with wild-type littermates at vertebral and femoral sites across the lifespan in both sexes. The magnitude of the vertebral trabecular phenotype increased with age, whereas age-related effects in the femur were more modest and site dependent. Vertebral micro-finite element analysis predicted greater stiffness and ultimate force in F318L/+ mice irrespective of age. Cortical thickness was modestly increased, particularly in female mice, but femoral mechanical properties were largely unchanged. The relative increase in vertebral trabecular bone was similar on the FVB/NJ and C57BL/6 backgrounds in males but greater on C57BL/6 in females, whereas the femoral trabecular and cortical responses were markedly attenuated on C57BL/6 in both sexes. In G213R/+ mice, the relative trabecular phenotype was similar on the C57BL/6 and 129 backgrounds, except for a greater vertebral phenotype in 129 males. Likewise, comparison of F318L/+ and G213R/+ mice demonstrated comparable vertebral phenotypes, although mutation-specific differences emerged at the femur, particularly in males. Conclusion: Collectively, these findings demonstrate that heterozygous Clcn7 mutations produce a robust osteopetrotic phenotype characterized primarily by increased trabecular bone mass that is present regardless of sex, age, genetic background, and mutation type. Age and genetic background modify its magnitude in a site- and sex-specific manner, suggesting that local factors may contribute more strongly to phenotypic variation than the specific disease-causing Clcn7 mutation. These results provide insight into determinants of phenotypic heterogeneity in ADOII and establish a framework for future mechanistic studies of osteopetrotic bone quality and fragility.

physiology↗

bioRxiv2025

Genetic analysis of triplicated genes affecting sex-specific skeletal deficits in Down syndrome model mice

Down syndrome (DS) is caused by the triplication of human chromosome 21 (Hsa21), resulting in skeletal insufficiency and altered bone development. DS mouse models recapitulate these deficits, including sexual dimorphism in long bone alterations. Historically, Ts65Dn mice provided much of the insight behind DS-related skeletal deficits with [~]100 trisomic orthologous genes, but there are concerns about genetic fidelity in this model due to included triplication of genes not homologous to Hsa21. A new DS mouse model, Ts66Yah, subtracted the non-Hsa21 homologous trisomic genes from Ts65Dn but has not been evaluated for long bone deficits. Comparing skeletal phenotypes between these models can indicate the contributions of non-Hsa21 trisomic genes and whether the Ts66Yah mouse is relevant as a model for DS-associated skeletal deficits. After assessing individual densitometric, morphometric, and mechanical variables in male and female Ts66Yah femurs at similar ages to when skeletal deficits had been observed in Ts65Dn mice, structural phenotypes were directly compared to those of Ts65Dn mice using a novel multivariate principal components analysis (PCA) method to generate composite scores. Overall, structural and mechanical bone phenotypes of the femur appear milder in Ts66Yah compared to Ts65Dn mice. The appearance of developmental trabecular microarchitecture deficits, but not other abnormalities, were evident earlier in Ts65Dn than Ts66Yah mice. Dyrk1a, a gene triplicated in both models, affected skeletal structure differently in each model, likely through differing gene interactions. The novel component score analysis incorporating PCA detected subclinical phenotypes lost in individual analyses, which could be advantageous when determining overall skeletal deficits. Article summaryMouse models are essential for understanding mechanisms behind human conditions, such as Down syndrome (DS). This study evaluates long bone morphology and strength at key timepoints of development in a new DS mouse model and introduces a novel method derived from principal component analysis (PCA) to compare phenotypes between two different DS models. While both models generally exhibit similar sex-specific deficits, the window of efficacy for genetic and pharmacological intervention on a therapeutic target varies. This illustrates the importance of validating DS phenotypes and mechanisms in multiple mouse models. The method developed could be used in broader scientific applications.

genetics↗

bioRxiv2021

Raloxifene reduces sex- and age-related intervertebral disc degeneration in mice by estrogen signaling

Estrogen agonist raloxifene is an FDA-approved treatment for osteoporosis in postmenopausal women that may also be a promising prophylactic for painful intervertebral disc (IVD) degeneration. Here, we hypothesized that raloxifene would augment IVD structure and reduce neurokinin-1 (substance P) in young and old mice by stimulating estrogen signaling. 2.5 month (male and female) and 22.5 month (female) C57Bl/6J mice were subcutaneously injected with raloxifene hydrochloride (5x/week, 6week, n=7-9/grp). Next, to determine the impact of estrogen-deficiency to IVD structure and substance P, female mice were ovariectomized (OVX) at 4mo and tissues from OVX and sham-operated mice were harvested at 6mo (n=5-6/grp). First, compared to male IVD, female IVD expressed less col2 and osterix transcription, early markers of IVD degeneration. Irrespective of sex, raloxifene increased the transcriptional expression for extracellular matrix anabolism, proliferation, notochordal cells (vs chondrocyte-like cells) and estrogen signaling in young IVD. Next, we determined that biological sex and aging each induced structural features of lumbar IVD degeneration. Therapeutically, injection of raloxifene countered these features by increasing IVD height in young mice, preventing mild sex-related IVD degeneration in young female mice and partially reversing age-related IVD degeneration in old female mice. Further, estrogen agonist raloxifene upregulated er- protein and downregulated substance P protein in young and old IVD. By contrast, estrogen-deficiency by OVX increased IVD degeneration and substance P protein in IVD cells. Similarly, substance P protein in vertebral osteocytes was upregulated in females relative to males and by estrogen-deficiency and downregulated by raloxifene. Overall, raloxifene augmented IVD structure and reduced substance P expression in young and old female murine IVD, whereas estrogen-deficiency increased substance P in the spine. These data suggest that raloxifene may potentially relieve painful IVD degeneration in postmenopausal women induced by biological sex, estrogen-deficiency and advanced age. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=71 SRC="FIGDIR/small/449482v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@87c74borg.highwire.dtl.DTLVardef@2d2bf8org.highwire.dtl.DTLVardef@1a1e365org.highwire.dtl.DTLVardef@15803e7_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract Injection of raloxifene promotes IVD health by engaging estrogen and Wnt signaling to promote cell proliferation and IVD structure. Differential estrogen signaling by raloxifene and ovariectomy regulated nerve signaling protein substance P in the spine. Raloxifene may also bind water to collagen to promote hydration. Acan: aggrecan, AF: annulus fibrosus, NC: notochordal cell, NP: nucleus pulposus C_FIG

bioengineering↗

bioRxiv2019

Mechanical Suppression of Breast Cancer Cell Invasion and Paracrine Signaling Requires Nucleo-Cytoskeletal Connectivity

Exercise benefits the musculoskeletal system and reduces the effects of cancer. The beneficial effects of exercise are multifactorial, where metabolic changes and tissue adaptation influence outcomes. Mechanical signals, a principal component of exercise, are anabolic to the musculoskeletal system and restrict cancer progression. We examined the mechanisms through which cancer cells sense and respond to mechanical signals. Low-magnitude, high-frequency signals were applied to human breast cancer cells in the form of low-intensity vibration (LIV). LIV decreased invasion through matrix and impaired secretion of osteolytic factors PTHLH, IL-11, and RANKL. Furthermore, paracrine signals from mechanically stimulated cancer cells, reduced osteoclast differentiation resorptive capacity. Physically disconnecting the nucleus by knockdown of SUN1 and SUN2 impaired the ability of LIV to suppress invasion and production of osteolytic factors. LIV also increased cell stiffness; an effect dependent on an intact LINC complex. These data show that mechanical signals alter the metastatic potential of human breast cancer cells, where the nucleus serves as a mechanosensory apparatus to alter cell structure and intercellular signaling.

cancer biology↗