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 (low bone mineral density) 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 the genetic fidelity in this model due to the included triplication of genes not homologous to Hsa21. A new DS 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 determine the contribution of non-Hsa21 homologous 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 ..., Six-, nine-, and sixteen-week-old Ts66Yah femurs were wrapped in parafilm to maintain hydration and single-scanned using a SkyScan 1172 µCT system (Bruker, Kontich, Belgium) with the following parameters: 60kV, 167uA, 885ms, 10-micron voxel size, Al 0.5mm filter, 0.7⁰ rotation step and frame averaging of two. Two hydroxyapatite phantoms (0.25 and 0.75g/cm3 CaHA) were used to calibrate bone mineral density for each scanning session.
Femurs from P36 mice were wrapped in parafilm and group-scanned (Kohler et al. 2021) using a SkyScan 1272 µCT system (Bruker, Kontich, Belgium) with the following parameters: 70kV, 142uA, 1265ms, 10-micron voxel size, Al 0.5mm filter, 0.7⁰ rotation step and frame averaging of two. Two hydroxyapatite phantoms (0.3 and 1.25g/cm3 CaHA) were used to calibrate bone mineral density for each scanning session. No unstandardized comparisons were made between scans from different µCT systems.
All scans were reconstructed using NRecon with the follow..., , # Genetic analysis of triplicated genes affecting sex-specific skeletal deficits in Down syndrome model mice:

posted on bioRxiv 1 Feb 2025, updated 2 Dec 2025

Three csv files contain all new data reported in manuscript

1\) 6_9_16_wk_Ts66Yah_compiled_data.csv

2\) P36_Ts66Yah_Dyrk1a_germline_reduction_compiled_data.csv

3\) P36_Ts66Yah_Dyrk1a_inhibition_treatment_compiled_data.csv

NA indicates data is not available due to a broken right femur.

Columns are as follows for 1):

Animal ID

Age of animal at dissection in weeks

Genotype

Sex where M = male and F = female

Body weight in grams (g)

Femoral length in millimeters (mm)

Bone mineral density (BMD) in g/cm^3

Bone volume fraction (BV/TV) in %

Trabecular thickness (Tb.Th) in mm

Trabecular separation (Tb.Sp) in mm

Trabecular number (Tb.N) in 1/mm

Total cross-sectional area (Tt.Ar) in mm^2

Marrow area (Ma.Ar) in mm^2

Cortical bone area (Ct.Ar) in mm^2

Cortical area fraction (Ct.Ar/Tt.Ar) in %

Cortical bone thickness (Ct.T..., ,

唐氏综合征（Down Syndrome, DS）是由人类21号染色体（human chromosome 21, Hsa21）三体引发的疾病，可导致骨骼发育不全（骨密度低下）及骨骼发育异常。唐氏综合征小鼠模型可复现此类病理缺陷，包括长骨改变的性别二态性。过往研究中，Ts65Dn小鼠因携带约100个三体同源基因，为DS相关骨骼缺陷的机制探索提供了大量关键见解，但该模型因包含非Hsa21同源的三体基因，其遗传保真度受到学界质疑。

新型唐氏综合征模型Ts66Yah从Ts65Dn基因组中移除了非Hsa21同源的三体基因，但尚未针对长骨缺陷开展相关评估。对比这两种模型的骨骼表型，可明确非Hsa21同源三体基因的具体贡献，并验证Ts66Yah小鼠能否作为DS相关骨骼缺陷的可靠研究模型。

研究人员对不同周龄的雌雄Ts66Yah小鼠股骨开展了骨密度计量学、形态计量学及力学参数分析……选取6周、9周及16周龄的Ts66Yah小鼠股骨，以封口膜（parafilm）包裹以维持组织湿度，使用SkyScan 1172微型计算机断层扫描（micro-computed tomography, µCT）系统（布鲁克公司，比利时孔蒂赫）进行单次扫描，扫描参数如下：管电压60kV、管电流167μA、曝光时间885ms、体素尺寸10微米、0.5mm铝滤片、0.7°旋转步幅、帧平均次数2次。每次扫描均使用2个羟基磷灰石体模（0.25及0.75g/cm³ 羟基磷灰石钙，CaHA）校准骨密度。

针对P36龄小鼠的股骨，同样以封口膜包裹并采用分组扫描方式（Kohler等，2021），使用SkyScan 1272 µCT系统（布鲁克公司，比利时孔蒂赫），扫描参数为：70kV、142μA、1265ms、10微米体素尺寸、0.5mm铝滤片、0.7°旋转步幅、帧平均次数2次。每次扫描使用2个羟基磷灰石体模（0.3及1.25g/cm³ CaHA）校准骨密度。不同µCT系统的扫描结果未进行非标准化对比。

所有扫描数据均通过NRecon软件完成重建……

# 唐氏综合征模型小鼠中影响性别特异性骨骼缺陷的三体基因遗传分析
本研究于2025年2月1日发布于bioRxiv预印本平台，2025年12月2日更新

本研究附带3个CSV格式文件，包含论文中所有新增实验数据：
1) 6_9_16_wk_Ts66Yah_compiled_data.csv
2) P36_Ts66Yah_Dyrk1a_germline_reduction_compiled_data.csv
3) P36_Ts66Yah_Dyrk1a_inhibition_treatment_compiled_data.csv

注：NA表示因右侧股骨损坏导致数据不可用。

以下为第1个文件的列字段说明：
Animal ID：动物编号
Age of animal at dissection in weeks：解剖时动物周龄
Genotype：基因型
Sex：性别，M代表雄性，F代表雌性
Body weight in grams (g)：体重（单位：克）
Femoral length in millimeters (mm)：股骨长度（单位：毫米）
Bone mineral density (BMD) in g/cm^3：骨密度（Bone Mineral Density, BMD，单位：g/cm³）
Bone volume fraction (BV/TV) in %：骨体积分数（Bone Volume Fraction, BV/TV，单位：%）
Trabecular thickness (Tb.Th) in mm：骨小梁厚度（Trabecular Thickness, Tb.Th，单位：毫米）
Trabecular separation (Tb.Sp) in mm：骨小梁分离度（Trabecular Separation, Tb.Sp，单位：毫米）
Trabecular number (Tb.N) in 1/mm：骨小梁数量（Trabecular Number, Tb.N，单位：1/毫米）
Total cross-sectional area (Tt.Ar) in mm^2：总横截面积（Total Cross-Sectional Area, Tt.Ar，单位：mm²）
Marrow area (Ma.Ar) in mm^2：骨髓腔面积（Marrow Area, Ma.Ar，单位：mm²）
Cortical bone area (Ct.Ar) in mm^2：皮质骨面积（Cortical Bone Area, Ct.Ar，单位：mm²）
Cortical area fraction (Ct.Ar/Tt.Ar) in %：皮质骨面积分数（Cortical Area Fraction, Ct.Ar/Tt.Ar，单位：%）
Cortical bone thickness (Ct.T...