Dosage-sensitive region causing locomotor dysfunction.

<p>Diagram on left shows Hsa21 indicating short and long arms separated by the centromere (oval), banding structure and length in Mb. The orthologous region of Mmu16 is indicated in grey and the regions of Mmu16 duplicated in Ts1Rhr, Dp4Tyb, Dp5Tyb and Dp6Tyb mouse models are indicated in black. On the right these duplicated regions are expanded and all known protein coding genes in these intervals and two microRNA genes (<i>Mir802</i> and <i>Gm23062</i>) are listed (mouse genome assembly GRCm38.p4). The locomotor defect assayed by Rotarod maps to a minimal interval resulting from the overlap of Ts1Rhr, Dp4Tyb and Dp5Tyb with genes in the interval indicated in blue. The <i>Dyrk1a</i> gene (bold) is required in 3 copies for the locomotor defect. Genes outside this region are listed in black.</p

No broad defect in sensory behavior in Tc1 or Dp1Tyb mice.

<p>Analysis of Tc1 (<b>a</b>-<b>e</b>) and Dp1Tyb (<b>f-k</b>) mice at 14 weeks (<b>a-d</b>, <b>f-j</b>), or 11 weeks (<b>e,k</b>). (<b>a,f</b>) Withdrawal latency of right and left hind paws in response to cold plate. (<b>b,g</b>) Withdrawal latency of right and left hind paws in response to radiant heat (Hargreaves test). (<b>c,h</b>) Force required for 50% withdrawal of right and left hind paws in response to punctate mechanical stimulation (Von Frey test). (<b>d,i</b>) Number of nocifensive behaviors as a function of time following formalin injection into hind paw. (<b>e</b>,<b>k</b>) Quantification of sensory neuron subpopulations in dorsal root ganglia taken from L3-L5 region of (<b>e</b>) Tc1 mice and (<b>k</b>) Dp1Tyb mice showing the proportion of DRG cell profiles positive for the indicated markers. (<b>j</b>) Score representing ability of WT or Dp1Tyb mice to walk up a tapered inclined beam; a higher score indicates better performance. All graphs show mean±SEM (<b>a-d</b>, n = 10; <b>e</b>, n = 5; <b>f-j</b>, n = 7; <b>k</b>, n = 5). Data analyzed with unpaired t-test, *p < 0.05.</p

Normal cerebellar anatomy in Dp(16)1Yey mice.

<p>(<b>a</b>-<b>e</b>) Analysis of cerebellar anatomy in Dp(16)1Yey mice at P6. (<b>a</b>) Cross section through cerebellum stained with H&E with expanded view showing small purple granule cells in the external granule layer (EGL) (arrow), Roman numerals indicate lobules, (<b>b</b>) area of cerebellum as % of whole brain, (<b>c</b>) width of the EGL, (<b>d</b>) linear density of Purkinje cells, (<b>e</b>) density of granule cells in the EGL. (<b>f</b>-<b>l</b>) Analysis of cerebellar anatomy in Dp(16)1Yey mice at 6 months of age. (<b>f</b>) Cross section through cerebellum stained with H&E with expanded view showing small purple granule cells in the granule cell layer (GCL) (arrow), Roman numerals indicate lobules, (<b>g</b>) linear density of Purkinje cells, (<b>h</b>) density of granule cells in the GCL, (<b>i</b>) width of the GCL, (<b>j</b>) width of the molecular layer (ML), (<b>k</b>) cross section of lobule IX showing the ML subdivided into base, tip and inner and outer regions, (<b>l</b>) density of interneurons in the whole ML of lobule IX or in the base, tip or inner regions subdivided as in <b>k</b>. In <b>b</b>-<b>d</b> and <b>g</b>-<b>j</b> values are shown for individual lobules as indicated and also averaged over all lobules analyzed (n = 9 WT, 13Ts(16)1Yey P6 whole brain area; n = 7 WT, 12 Dp(16)1Yey at P6 for all other measurements; n = 9 WT and Dp(16)1Yey at 6 months). All graphs show mean±SEM.</p

Decreased numbers of motor neurons in Tc1 and Dp(16)1Yey mice.

<p>(<b>a</b>-<b>e</b>) Analysis of Tc1 mice and WT littermate controls at the indicated ages (n = 4 WT, 5 Tc1 at 4 months; 4 WT, 5 Tc1 at 19 months). Maximum force production by (<b>a</b>) TA, (<b>b</b>) EDL, and (<b>c</b>) Soleus muscles in response to tetanic stimulation. (<b>d</b>) Typical motor unit recording traces in WT and Tc1 mice, showing stepwise increments in single twitch force production in response to increased stimulating intensity. The number of increments recorded is taken as the number of motor units. (<b>e</b>) Number of motor units in EDL muscles of indicated mice. (<b>f</b>) Nissl-stained lumbar spinal cord sections of WT and Tc1 mice at 19 months of age, with the sciatic motor pool indicated by a dashed line. Inset shows motor neurons in the sciatic pool. Scale bars, 100 μm, inset 50 μm. (<b>g</b>) Number of spinal cord motor neurons in WT and Tc1 mice at 6 months (n = 8 WT, 5 Tc1) and 19 months of age (n = 4 WT, 5 Tc1). (<b>h</b>) Sections of the EDL, TA and soleus muscles of WT and Tc1 mice at 19 months of age, stained for succinate dehydrogenase (SDH) at low (left) and high (right) magnification. Muscle fibers with dark blue staining have higher SDH activity and thus rely on oxidative phosphorylation and are more likely to be slow fibers. Clustering of darker fibers in Tc1 mice indicates denervation and subsequent reinnervation by slow motor neurons and a shift towards slower muscle fibers. Scale bars: low magnification, 500 μm; high magnification, 50 μm. (<b>i</b>) Number of motor neurons in WT and Tc1 mice at 22d of age (n = 4 WT, 6 Tc1). (<b>j, k</b>) Number of motor neurons in mice of the indicated genotypes and matched controls at 6 months of age (n = 6 WT, 6 Dp(16)1Yey, 8 Dp(16)1Yey/Dp(10)1Yey/Dp(17)1Yey triple trisomic; 7 WT, 7 Dp(10)1Yey; 6 WT, 6 Dp(17)1Yey). (<b>l</b>) Number of motor neurons in Dp(16)1Yey mice and controls at P6 (n = 5 WT, 5 Dp(16)1Yey). (<b>m</b>) Number of motor neurons in mice of the indicated genotypes and matched controls at 6 months of age (n = 6 WT, 7 Dp9Tyb; 7 WT, 7 Dp2Tyb; 8 WT, 10 Dp3Tyb). All graphs show mean±SEM. Data analyzed with unpaired t-test, *p < 0.05, **p < 0.001, ***p < 0.0001.</p

Decreased numbers of motor neurons in humans with DS.

<p>(<b>a</b>) Examples of human cervical spinal cord sections stained with Luxol Fast Blue. Dashed white circle indicates area containing motor neurons. Inset shows a higher magnification image of the ventral area containing motor neurons. Scale bar, 100 μm. (<b>b</b>) Number of motor neurons per hemisection of cervical spinal cord of adults with DS, ALS and controls (n = 4 control, 3 DS, 3 ALS). All graphs show mean±SEM. Data analyzed with unpaired t-test, **p < 0.01, ***p < 0.001.</p

Increased <i>Dyrk1a</i> expression in Dp(16)1Yey and Dp3Tyb mice.

<p>(<b>a-d</b>) Mean±SEM mRNA levels of <i>Dyrk1a</i>, <i>Gad1</i> and <i>Gad2</i> in the cerebellum of Dp(16)1Yey mice at 10 weeks (<b>a</b>) and 6 days (<b>b</b>) of age and in 10 week old Dp3Tyb (<b>c</b>) and Dp5Tyb (<b>d</b>) mice. Expression of the test gene was normalized to <i>Gapdh</i> and then to expression in WT control mice (n = 5 of each genotype). Data analyzed with unpaired t-test, *p < 0.05, **p < 0.01, ***p < 0.001.</p