GK2

Summary

GK2 (glycerol kinase 2, HGNC:4291) is a protein-coding gene on chromosome 4q21.21, encoding Glycerol kinase 2 (Q14410). Key enzyme in the regulation of glycerol uptake and metabolism.

Predicted to enable glycerol kinase activity. Predicted to be involved in several processes, including glycerol-3-phosphate biosynthetic process; sperm mitochondrial sheath assembly; and triglyceride metabolic process. Located in sperm midpiece.

Source: NCBI Gene 2712 — RefSeq curated summary.

At a glance

• Gene–disease (curated): Tourette syndrome (No Known Disease Relationship, GenCC)
• GWAS associations: 5
• Clinical variants (ClinVar): 69 total
• MANE Select transcript: NM_033214

Identifiers

Gene identifiers

Field	Value
HGNC ID	HGNC:4291
Approved symbol	GK2
Name	glycerol kinase 2
Location	4q21.21
Locus type	gene with protein product
Status	Approved
Aliases	GKTA
Ensembl gene	ENSG00000196475
Ensembl biotype	protein_coding
OMIM	600148
Entrez	2712

Gene structure

Transcript identifiers

Ensembl transcripts: 1 — 1 protein_coding

ENST00000358842

RefSeq mRNA: 1 — MANE Select: NM_033214 NM_033214

CCDS: CCDS3585

Canonical transcript exons

ENST00000358842 — 1 exons

Exon	Start	End
ENSE00001407062	79406361	79408228

Expression profiles

Bgee: expression breadth broad, 25 present calls, max score 94.24.

FANTOM5 (CAGE): breadth tissue_specific, TPM avg 0.1822 / max 153.8200, expressed in 4 samples.

FANTOM5 promoters (5 alternative TSS)

Promoter ID	TPM avg	Samples expressed
52737	0.1445	3
52738	0.0195	3
203261	0.0078	3
52740	0.0062	3
52739	0.0041	3

Top tissues by expression

258 total, by Bgee expression score (0-100, higher = more expressed):

Tissue	Anatomy ID	Expression score	Quality
sperm	CL:0000019	94.24	gold quality
left testis	UBERON:0004533	94.18	gold quality
right testis	UBERON:0004534	93.70	gold quality
male germ cell	CL:0000015	93.63	gold quality
testis	UBERON:0000473	91.73	gold quality
adult organism	UBERON:0007023	82.22	gold quality
pancreatic ductal cell	CL:0002079	73.29	silver quality
endometrium epithelium	UBERON:0004811	61.87	gold quality
mucosa of urinary bladder	UBERON:0001259	61.58	gold quality
tibialis anterior	UBERON:0001385	61.15	silver quality
ileal mucosa	UBERON:0000331	56.45	silver quality
cerebellar vermis	UBERON:0004720	54.61	gold quality
upper leg skin	UBERON:0004262	54.05	silver quality
deltoid	UBERON:0001476	52.76	gold quality
Brodmann (1909) area 10	UBERON:0013541	52.50	gold quality
metanephric glomerulus	UBERON:0004736	52.33	gold quality
quadriceps femoris	UBERON:0001377	52.24	gold quality
vastus lateralis	UBERON:0001379	51.13	gold quality
cervix squamous epithelium	UBERON:0006922	50.81	gold quality
frontal pole	UBERON:0002795	50.41	gold quality
middle frontal gyrus	UBERON:0002702	50.30	gold quality
paraflocculus	UBERON:0005351	50.18	gold quality
Brodmann (1909) area 46	UBERON:0006483	49.30	gold quality
hair follicle	UBERON:0002073	49.18	gold quality
thymus	UBERON:0002370	49.13	gold quality
layer of synovial tissue	UBERON:0007616	49.05	gold quality
kidney epithelium	UBERON:0004819	49.02	gold quality
olfactory bulb	UBERON:0002264	48.92	gold quality
myocardium	UBERON:0002349	48.87	gold quality
oviduct epithelium	UBERON:0004804	48.84	gold quality

Single-cell (SCXA)

Detected in 1 experiment(s), a significant marker in 1.

Experiment	Marker?	Max mean expression
E-ANND-3	yes	2.63

Regulation

Is transcription factor: no

miRNA regulators (miRDB)

9 targeting GK2, top 30 by miRDB confidence (max_score; target_count = how many genes the miRNA targets in total — lower means more specific):

miRNA	Max score	Avg score	miRNA target_count
HSA-MIR-8063	99.91	69.76	3146
HSA-MIR-4495	99.82	72.08	3080
HSA-MIR-1827	99.63	68.57	3265
HSA-MIR-4796-5P	99.34	70.06	810
HSA-MIR-4528	99.18	69.77	1936
HSA-MIR-11399	98.71	65.69	869
HSA-MIR-8078	98.32	65.73	361
HSA-MIR-5007-5P	97.95	64.71	614
HSA-MIR-125B-2-3P	96.69	68.38	1210

Literature-anchored findings (GeneRIF, showing 1)

• analysis of LGALS3, PHB2, MUC1, and GK2 expression with CA15-3 in early-stage breast cancer (PMID:26289852)

Cross-species orthologs

6 orthologs

Organism	Symbol	Gene ID
danio_rerio	GK2	ENSDARG00000053456
mus_musculus	Gk2	ENSMUSG00000050553
rattus_norvegicus	Gk2	ENSRNOG00000029397
drosophila_melanogaster	CG8298	FBGN0033673
drosophila_melanogaster	Gk2	FBGN0035266
caenorhabditis_elegans		WBGENE00020007

Paralogs (6): XYLB (ENSG00000093217), FGGY (ENSG00000172456), GK5 (ENSG00000175066), SHPK (ENSG00000197417), GK (ENSG00000198814), GK3 (ENSG00000229894)

Protein

Protein identifiers

Glycerol kinase 2 — Q14410 (reviewed: Q14410)

Alternative names: ATP:glycerol 3-phosphotransferase 2, Glycerol kinase, testis specific 2

All UniProt accessions (2): Q14410, A0A140VKG0

UniProt curated annotations — full annotation on UniProt →

Function. Key enzyme in the regulation of glycerol uptake and metabolism. Essential for male fertility and sperm mitochondrial sheath formation. Required for proper arrangement of crescent-like mitochondria to form the mitochondrial sheath during spermatogenesis. Can induce mitochondrial clustering through interactions with PLD6 and up-regulation of phosphatidic acid synthesis in the mitochondria.

Subunit / interactions. Interacts with ARMC12. Interacts with PLD6.

Subcellular location. Mitochondrion outer membrane. Cytoplasm.

Tissue specificity. Testis-specific. Expressed in the midpiece of spermatozoa.

Pathway. Polyol metabolism; glycerol degradation via glycerol kinase pathway; sn-glycerol 3-phosphate from glycerol: step 1/1.

Similarity. Belongs to the FGGY kinase family.

RefSeq proteins (1): NP_149991* (*=MANE)

Domains & families (InterPro)

ID	Name	Type
IPR000577	Carb_kinase_FGGY	Family
IPR005999	Glycerol_kin	Family
IPR018483	Carb_kinase_FGGY_CS	Conserved_site
IPR018484	FGGY_N	Domain
IPR018485	FGGY_C	Domain
IPR042018	GK1-3_metazoan-type	Family
IPR043129	ATPase_NBD	Homologous_superfamily

Pfam: PF00370, PF02782

Catalyzed reactions (Rhea), 1 shown:

• glycerol + ATP = sn-glycerol 3-phosphate + ADP + H(+) (RHEA:21644)

UniProt features (14 total): binding site 8, sequence conflict 4, chain 1, transmembrane region 1

Structure

Experimental structures (PDB)

0 structures.

Predicted structure (AlphaFold)

Model	pLDDT	Fraction very-high
AF-Q14410-F1	92.31	0.81

Functional residue map

Curated UniProt residues grouped by drug-discovery relevance — catalytic, ligand-binding, modification, and mutation-validated positions. Source: UniProtKB sequence features.

Ligand- & substrate-binding residues (8): 20; 24; 94; 148; 259; 281; 326; 427–431

Function

Pathways and Gene Ontology

Reactome pathways

1 pathways

ID	Pathway
R-HSA-75109	Triglyceride biosynthesis

MSigDB gene sets: 103 (showing top): GOBP_POLYOL_METABOLIC_PROCESS, GOBP_POLYOL_CATABOLIC_PROCESS, GOBP_ORGANOPHOSPHATE_METABOLIC_PROCESS, GOBP_MALE_GAMETE_GENERATION, GOBP_ORGANOPHOSPHATE_BIOSYNTHETIC_PROCESS, GOBP_CARBOHYDRATE_DERIVATIVE_METABOLIC_PROCESS, NKX61_01, GOBP_GLYCEROLIPID_METABOLIC_PROCESS, MORF_ZNF10, GOBP_CARBOHYDRATE_DERIVATIVE_BIOSYNTHETIC_PROCESS, GOBP_CILIUM_ORGANIZATION, KEGG_PPAR_SIGNALING_PATHWAY, GOBP_CILIUM_MOVEMENT, GOBP_CILIUM_OR_FLAGELLUM_DEPENDENT_CELL_MOTILITY, GOBP_CARBOHYDRATE_METABOLIC_PROCESS

GO Biological Process (10): glycerol metabolic process (GO:0006071), triglyceride metabolic process (GO:0006641), spermatogenesis (GO:0007283), glycerol catabolic process (GO:0019563), flagellated sperm motility (GO:0030317), glycerol-3-phosphate biosynthetic process (GO:0046167), sperm mitochondrial sheath assembly (GO:0120317), carbohydrate metabolic process (GO:0005975), glycerol-3-phosphate metabolic process (GO:0006072), cell differentiation (GO:0030154)

GO Molecular Function (7): glycerol kinase activity (GO:0004370), ATP binding (GO:0005524), nucleotide binding (GO:0000166), protein binding (GO:0005515), kinase activity (GO:0016301), transferase activity (GO:0016740), phosphotransferase activity, alcohol group as acceptor (GO:0016773)

GO Cellular Component (7): mitochondrion (GO:0005739), mitochondrial outer membrane (GO:0005741), extracellular exosome (GO:0070062), sperm midpiece (GO:0097225), sperm mitochondrial sheath (GO:0097226), cytoplasm (GO:0005737), membrane (GO:0016020)

Reactome top-level categories

Rollup of top-1 pathways:

Category	Pathways
Triglyceride metabolism	1

GO top-level categories

Rollup of top GO terms by namespace:

Category	Terms
cellular anatomical structure	4
transferase activity, transferring phosphorus-containing groups	2
carbohydrate metabolic process	1
polyol metabolic process	1
acylglycerol metabolic process	1
developmental process involved in reproduction	1
male gamete generation	1
glycerol metabolic process	1
alditol catabolic process	1
cilium-dependent cell motility	1
cilium movement involved in cell motility	1
sperm motility	1
glycerol-3-phosphate metabolic process	1
organophosphate biosynthetic process	1
carbohydrate derivative biosynthetic process	1
cellular component assembly	1
sperm flagellum assembly	1
primary metabolic process	1
alditol phosphate metabolic process	1
cellular developmental process	1
kinase activity	1
phosphotransferase activity, alcohol group as acceptor	1
adenyl ribonucleotide binding	1
purine ribonucleoside triphosphate binding	1
nucleoside phosphate binding	1
heterocyclic compound binding	1
binding	1
catalytic activity	1
cytoplasm	1
intracellular membrane-bounded organelle	1
mitochondrial membrane	1
organelle outer membrane	1
extracellular vesicle	1
sperm flagellum	1
sperm midpiece	1
intracellular anatomical structure	1

Protein interactions and networks

STRING

1910 interactions, top by confidence (×1000):

Protein A	Protein B	Partner UniProt	Score
GK2	VDAC3	Q9Y277	962
GK2	VDAC1	P21796	945
GK2	VDAC2	P45880	822
GK2	LPL	P06858	770
GK2	AQP9	O43315	760
GK2	NR0B1	P51843	751
GK2	AQP3	Q92482	722
GK2	TPI1	P00938	706
GK2	GUK1	Q16774	683
GK2	CS	O75390	629
GK2	PC	P11498	629
GK2	PXDN	Q92626	627
GK2	PXDNL	A1KZ92	626
GK2	CEL	P19835	600
GK2	STAR	P49675	596

IntAct

7 interactions, top by confidence:

A	B	Type	Score
GK	GK2	psi-mi:“MI:0915”(physical association)	0.590
GK2	GK	psi-mi:“MI:0915”(physical association)	0.590
GK2	HSPA8	psi-mi:“MI:0915”(physical association)	0.400
HSCB	RBP5	psi-mi:“MI:0914”(association)	0.350
SLAMF1	ZNF292	psi-mi:“MI:0914”(association)	0.350
GK3	APOD	psi-mi:“MI:0914”(association)	0.350

BioGRID (12): GK2 (Affinity Capture-MS), GK2 (Co-fractionation), GK2 (Synthetic Growth Defect), HSPA8 (Affinity Capture-MS), GK2 (Affinity Capture-MS), GK2 (Affinity Capture-MS), GK2 (Affinity Capture-MS), GK2 (Affinity Capture-MS), GK2 (Affinity Capture-MS), GK2 (Proximity Label-MS), GK2 (Proximity Label-MS), GK2 (Proximity Label-MS)

ESM2 similar proteins: A0A0U1WZ18, A3QK15, B9N1F9, D3ZVR9, E0CSI1, O70196, P00503, P00504, P05201, P08906, P33121, P33124, P40142, P50137, P50554, P54767, P61922, P78330, P80147, Q07346, Q14410, Q15124, Q1W377, Q28BL6, Q2KHU0, Q2KIG0, Q42472, Q42521, Q4R4D5, Q4R5L1, Q5R691, Q5RB83, Q5ZLG0, Q6P1N9, Q6P8M1, Q7TN78, Q80W40, Q86V21, Q8BZF8, Q8K183

Diamond homologs: A0KAA1, A0KIT3, A1R6X6, A1TGD7, A3QIN4, A4FNR2, A4JHM8, A4SPA7, A4T5Y1, A5CS23, A5G146, A5U920, A5UU55, A5VE44, A5VZG7, A6M1Y8, A6WIC0, A6WXV2, A8F679, A8FQ89, A8H995, A8I8V7, A9AFH2, A9KY18, A9W8T7, A9WJ21, A9WS93, B0K643, B0KUG0, B0RMN0, B0TQM6, B1JY43, B1KKY8, B1LWN6, B1MFT1, B1YWB2, B1ZGW7, B2IE09, B2SYH7, B7KN92

SIGNOR signaling

0 interactions.

Disease & clinical

Clinical variants and AI predictions

ClinVar

69 variants total. Per-class counts are floors (≥ shown; pagination cap):

Classification	Count (floor)
Pathogenic	0
Likely pathogenic	0
Uncertain significance	65
Likely benign	3
Benign	0

Top pathogenic / likely-pathogenic (0)

SpliceAI

0 predictions. Top by Δscore:

AlphaMissense

3619 scored. Top likely-pathogenic:

Variant	Protein change	am_pathogenicity
4:79407119:A:T	V361D	0.997
4:79407558:A:G	W215R	0.996
4:79407558:A:T	W215R	0.996
4:79407751:A:C	S150R	0.995
4:79407751:A:T	S150R	0.995
4:79407753:T:G	S150R	0.995
4:79407069:C:A	G378W	0.994
4:79407104:C:T	G366E	0.994
4:79406694:A:G	W503R	0.993
4:79406694:A:T	W503R	0.993
4:79406886:C:G	A439P	0.993
4:79407556:C:A	W215C	0.993
4:79407556:C:G	W215C	0.993
4:79407006:C:G	A399P	0.992
4:79407068:C:T	G378E	0.992
4:79407069:C:G	G378R	0.992
4:79407069:C:T	G378R	0.992
4:79407105:C:A	G366W	0.992
4:79407349:G:C	F284L	0.992
4:79407349:G:T	F284L	0.992
4:79407351:A:G	F284L	0.992
4:79407592:A:C	S203R	0.992
4:79407592:A:T	S203R	0.992
4:79407594:T:G	S203R	0.992
4:79406692:C:A	W503C	0.991
4:79406692:C:G	W503C	0.991
4:79407210:A:G	W331R	0.991
4:79407210:A:T	W331R	0.991
4:79407847:T:A	R118S	0.991
4:79407847:T:G	R118S	0.991

dbSNP variants (sampled 300 via entrez): RS1000185205 (4:79408207 A>C,G,T), RS1000217797 (4:79408362 C>G), RS1001851314 (4:79406653 A>T), RS1002632383 (4:79409798 G>A), RS1002663442 (4:79410107 T>C), RS1002875280 (4:79407017 G>A), RS1003950564 (4:79408289 A>G), RS1004199992 (4:79405959 A>G), RS1005241146 (4:79407084 C>A,T), RS1005706572 (4:79408369 T>C), RS1007714638 (4:79409147 T>A), RS1008265213 (4:79408761 A>G), RS1008375938 (4:79406286 A>C), RS1009252675 (4:79406323 C>G,T), RS1010192507 (4:79408148 T>C,G)

Disease associations

OMIM: gene MIM:600148 | disease phenotypes:

GenCC curated gene-disease

Disease	Classification	Inheritance
Tourette syndrome	No Known Disease Relationship	Unknown

Mondo (2): primary ovarian failure (MONDO:0005387), Tourette syndrome (MONDO:0007661)

Orphanet (1): NON RARE IN EUROPE: Primary ovarian failure (Orphanet:619)

HPO phenotypes

0 total (0 of 0 shown, HPO-id order):

GWAS associations

5 associations (top):

Study	Trait	p-value
GCST003997_43	Myopia	3.000000e-15
GCST007327_61	Smoking status (ever vs never smokers)	4.000000e-08
GCST009007_6	High-grade serous ovarian cancer	9.000000e-07
GCST009391_2036	Metabolite levels	3.000000e-06
GCST010002_9	Refractive error	2.000000e-65

EFO canonical traits (2, from GWAS)

EFO ID	Trait name
EFO:0004318	smoking behavior
EFO:1001516	ovarian serous carcinoma

MeSH disease descriptors (2)

Descriptor	Name	Tree numbers
D016649	Primary Ovarian Insufficiency	C12.050.351.500.056.630.750; C12.100.250.056.630.750; C19.391.630.750
D005879	Tourette Syndrome	C10.228.140.079.898; C10.228.662.825.800; C10.574.500.850; C16.320.400.820; F03.625.992.850

Drugs & pharmacology

Drug and pharmacology data

Is drug target: no

PharmGKB: 1 entry (VIP=true, CPIC=false)

CTD chemical–gene interactions

8 total (human), top 8 by PubMed support.

Chemical	Actions (top 5)	PubMed papers
hydroxyhydroquinone	increases expression	1
CGP 52608	affects binding, increases reaction	1
Benzo(a)pyrene	increases methylation	1
Cadmium	decreases expression, increases abundance	1
Tretinoin	increases expression	1
Valproic Acid	decreases methylation	1
Cadmium Chloride	decreases expression, increases abundance	1
Copper Sulfate	increases expression	1

Clinical trials (associated diseases)

258 trials via MONDO — disease-level, not drug-specific.

Trial	Phase	Status	Title
NCT00152750	PHASE4	UNKNOWN	Study of Clonidine on Sleep Architecture in Children With Tourette’s Syndrome (TS) and Comorbid ADHD
NCT00226824	PHASE4	TERMINATED	Safety Study of Galantamine in Tic Disorders
NCT00241176	PHASE4	COMPLETED	Open Label Trial of Aripiprazole in Children and Adolescents With Tourette’s Disorder
NCT00370838	PHASE4	COMPLETED	Comparison of Keppra and Clonidine in the Treatment of Tics
NCT01018056	PHASE4	COMPLETED	Developing New Treatments for Tourette Syndrome: Therapeutic Trials With Modulators of Glutamatergic Neurotransmission
NCT01547000	PHASE4	COMPLETED	Guanfacine in Children With Tic Disorders
NCT03239210	PHASE4	COMPLETED	Effects of Ondansetron in Obsessive-compulsive and Tic Disorders
NCT00417066	PHASE4	COMPLETED	Flexible GnRH Antagonist vs Flare up GnRH Agonist Protocol in Poor Responders
NCT00732693	PHASE4	COMPLETED	Evaluation of Physiologic and Standard Sex Steroid Replacement Regimens in Women With Premature Ovarian Failure
NCT00837616	PHASE4	COMPLETED	Estrogen Dosing in Turner Syndrome: Pharmacology and Metabolism
NCT01853501	PHASE4	UNKNOWN	Effects of ADSC Therapy in Women With POF
NCT02783937	PHASE4	COMPLETED	Filgrastim for Premature Ovarian Insufficiency
NCT03535480	PHASE4	UNKNOWN	Autologous Bone Marrow Stem Cell Ovarian Transplantation to Restore Ovarian Function in Premature Ovarian Failure
NCT00004376	PHASE3	COMPLETED	Phase III Randomized, Double-Blind, Placebo-Controlled Study of Guanfacine for Tourette Syndrome and Attention Deficit Hyperactivity Disorder
NCT00206323	PHASE3	COMPLETED	A Randomized, Placebo-controlled, Tourette Syndrome Study.
NCT00206336	PHASE3	COMPLETED	An Open-label Study to Determine the Efficacy and Safety of Topiramate in the Treatment of Tourette Syndrome.
NCT00478842	PHASE3	COMPLETED	Pallidal Stimulation and Gilles de la Tourette Syndrome
NCT00681863	PHASE3	TERMINATED	Open-label Extension Study of Pramipexole in the Treatment of Children and Adolescents With Tourette Syndrome
NCT01501695	PHASE3	COMPLETED	Phase III Study of 5LGr to Treat Tic Disorder
NCT03087201	PHASE3	COMPLETED	CANNAbinoids in the Treatment of TICS (CANNA-TICS)
NCT03487783	PHASE3	COMPLETED	Aripiprazole Oral Solution in the Treatment of Children and Adolescents With Tourette’s Syndrome
NCT03567291	PHASE3	TERMINATED	Evaluation of Safety and Tolerability of Long-term TEV-50717 (Deutetrabenazine) for Treatment of Tourette Syndrome in Children and Adolescents
NCT03571256	PHASE3	COMPLETED	A Study to Test if TEV-50717 is Effective in Relieving Tics Associated With Tourette Syndrome (TS)
NCT06021522	PHASE3	ACTIVE_NOT_RECRUITING	A Study to Evaluate Long-term Safety of Ecopipam Tablets in Children, Adolescents and Adults With Tourette’s Disorder
NCT00140998	PHASE3	COMPLETED	Estrogen Treatment (Oral vs. Patches) in Turner Syndrome
NCT00004393	PHASE2	COMPLETED	Phase II Double Blind Placebo Controlled Trial of Risperidone in Tourette Syndrome
NCT00004652	PHASE2	COMPLETED	Phase II Pilot Controlled Study of Short Vs Longer Term Pimozide (Orap) Therapy in Tourette Syndrome
NCT00231985	PHASE2	COMPLETED	Effectiveness of Behavior Therapy and Psychosocial Therapy for the Treatment of Tourette Syndrome and Chronic Tic Disorder
NCT00311909	PHASE2	COMPLETED	Thalamic Deep Brain Stimulation for Tourette Syndrome
NCT00529308	PHASE2	COMPLETED	Transcranial Magnetic Stimulation (TMS) for Individuals With Tourette’s Syndrome
NCT00558467	PHASE2	COMPLETED	Pramipexole Pilot Phase II Study in Children and Adolescents With Tourette Disorder According to DSM-IV Criteria
NCT01043549	PHASE2	TERMINATED	Repetitive Transcranial Magnetic Stimulation of the Posterior Parietal Cortex in Patients Suffering From Gilles de la Tourette Syndrome
NCT01133353	PHASE2	WITHDRAWN	A Study of the Effectiveness and Safety of Tetrabenazine MR in Pediatric Subjects With Tourette’s Syndrome
NCT01475383	PHASE2	WITHDRAWN	Study Evaluating The Safety And Efficacy Of PF-03654746 In Adult Subjects With Tourette’s Syndrome
NCT01647269	PHASE2	COMPLETED	A Trial of Bilateral Deep Brain Stimulation to the Globus Pallidus Internum in Tourette Syndrome
NCT01904773	PHASE2	COMPLETED	Safety, Tolerability, Pharmacokinetic, and Efficacy Study of AZD5213 in Adolescents With Tourette’s Disorder
NCT02102698	PHASE2	COMPLETED	Ecopipam Treatment of Tourette’s Syndrome in Subjects 7-17 Years
NCT02217007	PHASE2	WITHDRAWN	A Trial Evaluating the Efficacy, Safety, and Pharmacokinetics of SNC-102 in Subjects With Tourette Syndrome
NCT02247206	PHASE2	COMPLETED	VoIP Delivered Behavior Therapy for Tourette Syndrome
NCT02581865	PHASE2	COMPLETED	Safety and Efficacy Study of NBI-98854 in Adults With Tourette Syndrome