Supplementary table I Human fibroblasts and HD patients’ statistics. Age at biopsy indicates the age of the patients when skin fibroblasts were donated. N/A, non- applicable.

Age at Patient I.D. Gender (CAG)n Age of onset biopsy (yrs)

C1 (control) 36 Male Normal N/A C2 (control) 15 Male Normal N/A HD45 35 Male 21/45 unknown HD50 11 Male 20/50 26 years HD61 29 Female 20/61 18 years HD86 10 Male 22/86 2 years

Supplementary table II of the biosynthetic pathway analyzed by qPCR and sequence of primers used in the analysis.

GeneBank Name Mouse Sequence Accession #

NM_011673 Ugcg Fwd 5’ TTG TTC GGC TTC GTG CTC TT 3’ Rev 5’ GAG ACA CCA GGG AGC TTG CT 3’

NM_011375 St3gal5 Fwd 5’ ATA TGC TGC CCG AAC ATG ACT 3’ Rev 5’ CAA CTG GCG CAC TGT TCA AC 3’

NM_008080 B4galnt1 Fwd 5’ CCA GCC CAG TTC TGG ATA AAC T 3’ Rev 5’ GGT TGG GAG GGT GTC TTA CGA 3’

NM_019420 B3galt4 Fwd 5’ GGC AGT GCC CCT TCT GTA TTT 3’ Rev 5’ CGA GGC ATA GGG TGG AAA AG 3’

NM_009179 St3gal2 Fwd 5’ CAC CCT GAC TCG GCT GCT T 3’ Rev 5’ TCT CGC GCC TTA GGG CTA A 3’

NM_011374 St8sia1 Fwd 5’ TCC AGC TGC CAT TGA AGA AA 3’ Rev 5’ TGG ACC CGA CAT CTC TGG TGT A 3’

NM_009182 St8sia3 Fwd 5’ CCA GTC ATT TGT GCC CAT TAC 3’ Rev 5’ GGG ACC GGA AGT TAT TGC TA 3’

NM_008907 Cyp A Fwd 5’ TCC AAA GAC AGC AGA AAA CTT TCG 3’ Rev 5’ TCT TCT TGC TGG TCT TGC CAT TCC 3’

GeneBank Gene Name Human Sequence Accession #

NM_003782 B3GALT4 Fwd 5’ GGC CCG ATA CGT CCT CAA G 3’ Rev 5’ CAA AAC CTG GCC TCC TTC CT 3’

NM_021130 CYP A Fwd 5’ CCC ATT TGC TCG CAG TAT CC 3’ Rev 5’ GGA AAA CAT GGA ACC CAA AGG 3’

GeneBank Gene Name Rat Sequence Accession #

NM_133553.2 B3galt4 Fwd 5’ CCA GAG TCC CGG CAT CAC 3’ Rev 5’ GGC GTA GGG TGG GAA AGG 3’

NM_012583.2 HPRT Fwd 5’ ACA GCC CCA AAA TGG TTA AGG T 3’ Rev 5’ GGC TTT TCC ACT TTC GCT GAT G 3’

SUPPLEMENTARY FIGURE LEGENDS

SUPPLEMENTARY FIGURE 1

A) Analysis of ganglioside in the hippocampus of YAC128 mice by quantitative PCR. Data represent the mean expression (as ratios over wild- type) measured in five 6 month-old YAC128 mice compared to the same number of wild-type littermates. Gene expression was normalized over cyclophilin A expression.

No significant difference between WT and YAC128 mice was found. B) B3galt4

(GM1 synthase) expression and C) total GM1 content in the spleen of YAC128 mice. Analysis was performed in three 5-7 month-old YAC128 mice and three age- matched wild-type littermates. No statistically significant difference was found between WT and YAC128 mice.

SUPPLEMENTARY FIGURE 2

Dose-dependency and time-course of GM1 anti-apoptotic action in knock-in striatal cells. A) Cells were incubated in serum-free medium at 39ºC to induce apoptosis, in the presence of the indicated concentration of GM1. After 6 h, apoptosis was measured by Annexin-V binding and FACS analysis. B) GM1 incorporation into the cell plasma membrane was measured by cholera toxin B binding assay and FACs analysis. C) Cells were incubated as indicated in (A) in the presence or absence of 50

µM GM1. Apoptosis was assessed by Annexin-V binding and FACS analysis at the indicated time, over a period of 24 h. Data are reported as mean values ± SD. 7/7,

STHdh7/7; 111/111, STHdh111/111; *, p<0.05; **, p<0.001

SUPPLEMENTARY FIGURE 3

The protective effect of GM1 in striatal cells is not mediated by activation of Trk receptors. Cells were pre-incubated for 2 h with 200 nM K252a, a pan-Trk inhibitor, before GM1 administration and exposure to apoptotic stress (serum-free medium at

39ºC). Data are the mean ± SD of 3 experiments, each performed in triplicate. 7/7,

STHdh7/7; 111/111, STHdh111/111; *, p<0.05; **, p<0.001; ***, p<0.0001

SUPPLEMENTARY FIGURE 4

The GM1 analogue LIGA-20 does not protect knock-in HD cells from apoptosis.

A) Cells were exposed to apoptotic conditions in the presence or absence of 1 µM

LIGA-20 as described in Materials and Methods. Apoptosis was measured by annexin

V binding assay and FACS analysis at the indicated time-points. B) Cells were exposed to apoptotic conditions as described in Materials and Methods, in the presence of increasing concentration of LIGA-20. Levels of active caspase 3 were measured after 5 hours by in-cell western, using a LICOR Odyssey Infrared Image

System and according to the manufacturer’s instructions. Active caspase-3 levels were normalized over tubulin. Data are reported as mean values ± SD. 7/7, STHdh7/7;

111/111, STHdh111/111