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Gene

HTT

huntingtin

Summary

Cytogenetic location
4p16.3
Coordinates
Chromosome 4: 3,074,681–3,243,957 (GRCh38)
Exons
67 exons across 169.3 kb
Protein
3,142 amino acids
Inheritance
Autosomal dominant
Also known as
IT15
Previous symbols
HD
MANE Select transcript
ENST00000355072.11NM_001388492.1
Locus type
gene with protein product

Reference genomeGRCh38

Positions on gene and variant pages follow this choice, in this browser.

Curated report relevant to this gene

  • Huntington Disease

    • Autosomal dominant

      A progressive neurodegenerative disorder caused by HTT CAG-repeat expansion, with chorea, cognitive decline and psychiatric symptoms.

      • ClinGen rates the link definitive
      • 3 GenCC submitters rate it definitive or strong
      What knowing changes

      Genetic counseling and presymptomatic testing, antisense oligonucleotide therapies, dopaminergic and psychiatric medications, neuroprotection trials, reproductive counseling

Inheritance

Autosomal dominant
One changed copy, from either parent, is enough. A parent who has one passes it on to each child with a one-in-two chance.

How HTT is laid out

  • Coding sequence
  • Untranslated region
  • Intron
  • Direction of transcription
  • Known disease-causing sites
  • Stretches short reads find hard
Chromosome 4, with a bracket where HTT sits. HTT and 12 genes near it on chromosome 4, from 2,659,319 to 3,659,318.Chromosome 44p16.3p16.3p16.2p16.1p15.33p15.32p15.31p15.2p15.1p14p13p12p11q11q12q13.1q13.2q13.3q21.1q21.21q21.22q21.23q21.3q22.1q22.2q22.3q23q24q25q26q27q28.1q28.2q28.3q31.1q31.21q31.22q31.23q31.3q32.1q32.2q32.3q33q34.1q34.2q34.3q35.1q35.22.8 Mb3 Mb3.2 Mb3.4 Mb3.6 MbFAM193A: 2,536,572–2,732,576, forward strandFAM193ATNIP2: 2,741,648–2,756,406, reverse strandTNIP2SH3BP2: 2,793,015–2,841,291, forward strandSH3BP2ADD1: 2,843,576–2,930,082, forward strandADD1SLC75A1: 2,929,917–2,935,462, reverse strandSLC75A1NOP14: 2,937,925–2,963,502, reverse strandNOP14GRK4: 2,963,571–3,040,760, forward strandGRK4HTT: 3,074,681–3,243,957, forward strandHTTMSANTD1: 3,244,369–3,271,738, forward strandMSANTD1RGS12: 3,292,982–3,439,913, forward strandRGS12HGFAC: 3,441,924–3,449,493, forward strandHGFACDOK7: 3,463,190–3,501,540, forward strandDOK7LRPAP1: 3,503,612–3,532,446, reverse strandLRPAP1Diagram of HTT: 67 exons on the forward strand of chromosome 4Exon 1: 3 known disease-causing sitesExon 50: 1 known disease-causing siteExon 1: 3,074,681–3,075,088, 408 basesExon 2: 3,086,939–3,087,022, 84 basesExon 3: 3,099,274–3,099,394, 121 basesExon 4: 3,103,824–3,103,883, 60 basesExon 5: 3,105,357–3,105,436, 80 basesExon 6: 3,107,285–3,107,423, 139 basesExon 7: 3,115,304–3,115,445, 142 basesExon 8: 3,116,085–3,116,263, 179 basesExon 9: 3,121,228–3,121,432, 205 basesExon 10: 3,122,889–3,122,936, 48 basesExon 11: 3,125,549–3,125,629, 81 basesExon 12: 3,127,264–3,127,604, 341 basesExon 13: 3,129,924–3,130,047, 124 basesExon 14: 3,130,305–3,130,423, 119 basesExon 15: 3,131,286–3,131,397, 112 basesExon 16: 3,131,638–3,131,775, 138 basesExon 17: 3,132,562–3,132,720, 159 basesExon 18: 3,132,814–3,132,911, 98 basesExon 19: 3,134,401–3,134,540, 140 basesExon 20: 3,135,904–3,135,967, 64 basesExon 21: 3,136,226–3,136,326, 101 basesExon 22: 3,140,510–3,140,656, 147 basesExon 23: 3,142,766–3,142,886, 121 basesExon 24: 3,145,152–3,145,228, 77 basesExon 25: 3,146,797–3,146,948, 152 basesExon 26: 3,148,005–3,148,207, 203 basesExon 27: 3,154,293–3,154,419, 127 basesExon 28: 3,157,072–3,157,199, 128 basesExon 29: 3,160,282–3,160,392, 111 basesExon 30: 3,172,320–3,172,397, 78 basesExon 31: 3,172,908–3,173,131, 224 basesExon 32: 3,174,721–3,174,799, 79 basesExon 33: 3,174,946–3,175,107, 162 basesExon 34: 3,177,332–3,177,387, 56 basesExon 35: 3,178,298–3,178,446, 149 basesExon 36: 3,180,515–3,180,651, 137 basesExon 37: 3,182,354–3,182,470, 117 basesExon 38: 3,186,597–3,186,719, 123 basesExon 39: 3,187,651–3,187,886, 236 basesExon 40: 3,188,951–3,189,093, 143 basesExon 41: 3,199,732–3,199,939, 208 basesExon 42: 3,204,007–3,204,148, 142 basesExon 43: 3,206,496–3,206,675, 180 basesExon 44: 3,206,807–3,206,983, 177 basesExon 45: 3,207,281–3,207,357, 77 basesExon 46: 3,208,773–3,208,911, 139 basesExon 47: 3,209,827–3,209,949, 123 basesExon 48: 3,211,929–3,212,142, 214 basesExon 49: 3,212,564–3,212,709, 146 basesExon 50: 3,213,958–3,214,135, 178 basesExon 51: 3,215,110–3,215,211, 102 basesExon 52: 3,217,765–3,217,952, 188 basesExon 53: 3,220,182–3,220,308, 127 basesExon 54: 3,222,387–3,222,487, 101 basesExon 55: 3,223,406–3,223,560, 155 basesExon 56: 3,223,992–3,224,131, 140 basesExon 57: 3,225,661–3,225,743, 83 basesExon 58: 3,228,615–3,228,745, 131 basesExon 59: 3,228,880–3,229,009, 130 basesExon 60: 3,229,887–3,230,042, 156 basesExon 61: 3,233,163–3,233,353, 191 basesExon 62: 3,235,284–3,235,398, 115 basesExon 63: 3,235,565–3,235,778, 214 basesExon 64: 3,236,149–3,236,254, 106 basesExon 65: 3,238,447–3,238,609, 163 basesExon 66: 3,238,818–3,238,978, 161 basesExon 67: 3,239,846–3,243,957, 4,112 bases1102030405060675′3′

Exons of the gene's MANE Select transcript (release v1.5), from NCBI and EMBL-EBI, on the GRCh38 reference genome.

Chromosome bands from UCSC's GRCh38 ideogram (2022-10-29).

Nearby genes from Ensembl release 116, on GRCh38.

Exons make up 13.5 kb of the gene's 169.3 kb; 9,429 of those bases code for the protein.

How a genome test reads HTT

4

positions in HTT where ClinVar classes a change as pathogenic or likely pathogenic

None of them falls in a region short reads find hard.

A whole genome covers all 169.3 kb of HTT, introns included, not only the 13.5 kb of exons.

Where this comes from

  • HGNC: the gene's symbol, name, other symbols and location.
  • MANE Select v1.5, from NCBI and EMBL-EBI: the transcript, its exons and coding sequence.
  • GenCC and ClinGen, released 2026-10-16: which conditions the gene is linked to, and how strongly.
  • The ACMG secondary findings list, SF v3.2.
  • ClinVar and the GIAB stratifications: known disease-causing sites, and the regions short reads find hard.
  • The Human Phenotype Ontology, release 2026-09-01: the traits linked to the gene. Find out more at hpo.jax.org.
  • Data release 2026.10.16-c6eea6bf.

Cite this page

APA

Dante Labs. (n.d.). HTT gene: huntingtin. Retrieved 16 October 2026, from https://dantelabs.com/genes/htt

Vancouver

Dante Labs. HTT gene: huntingtin [Internet]. [cited 16 October 2026]. Available from: https://dantelabs.com/genes/htt

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