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DHCR7

7-dehydrocholesterol reductase

The DHCR7 gene provides instructions for an enzyme crucial in cholesterol production, and pathogenic variants in this gene are associated with Smith-Lemli-Opitz syndrome. DHCR7 encodes the enzyme 7-dehydrocholesterol reductase, which plays a vital role in the final step of cholesterol biosynthesis.

Chromosome 11q13.4 Autosomal recessive HGNC:2860 Tier C
DHCR7 11q13.4 p arm q arm 11

DHCR7 is located on the long (q) arm of chromosome 11, at band 11q13.4. Arm ratio per GRCh38 - banding schematic.

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Clinical tests that include this

Carrier Screening panel
DHCR7 is 1 of 1,008 genes on this panel
Expanded carrier screening for recessive and X-linked conditions

Overview

The DHCR7 gene, also known as 7-dehydrocholesterol reductase, is central to the human body's cholesterol synthesis pathway. It provides the genetic blueprint for an enzyme responsible for converting 7-dehydrocholesterol into cholesterol. Cholesterol itself is a fundamental molecule with diverse roles, from structural components in cell membranes to precursors for hormones and bile acids.

Pathogenic variants within the DHCR7 gene can impair this crucial enzymatic step, leading to a deficiency in cholesterol and an accumulation of its precursor, 7-dehydrocholesterol. This biochemical imbalance underpins the developmental and physiological features observed in associated genetic conditions.

What the gene does

The primary function of the DHCR7 gene is to direct the synthesis of 7-dehydrocholesterol reductase, an enzyme pivotal to the production of cholesterol. Specifically, this enzyme facilitates the final catalytic step in the cholesterol biosynthesis pathway, converting 7-dehydrocholesterol into cholesterol. Cholesterol is an indispensable waxy, fat-like substance that the body either produces or obtains from dietary sources.

Beyond its structural role in cell membranes, cholesterol is critical for embryonic development, influencing the signalling proteins that guide the early formation of the brain, limbs, and other key structures. It is also a component of myelin, the insulating sheath around nerve cells, and acts as a precursor for various hormones and digestive bile acids. Consequently, proper DHCR7 function is fundamental for overall physiological development and maintenance.

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Chromosome location

The DHCR7 gene is situated on chromosome 11, specifically at band 11q13.4. The full-length protein produced from this gene consists of 475 amino acids. This chromosomal location is consistent across the human genome, positioning DHCR7 as an important genetic locus for cholesterol metabolism.

Protein structure

The DHCR7 protein, 7-dehydrocholesterol reductase, is composed of 475 amino acids. Structural analysis indicates the presence of a Disordered region spanning amino acids 1-21. This region suggests flexibility and potential for various protein-protein interactions or regulatory roles, although its precise functional implications require further investigation.

Key variants

Variants in the DHCR7 gene encompass a range of genetic alterations that can affect the function of the 7-dehydrocholesterol reductase enzyme. These changes can impair the enzyme's ability to convert 7-dehydrocholesterol into cholesterol, leading to a spectrum of clinical consequences. The specific impact of a variant often depends on its type, location within the gene, and the resulting effect on protein activity.

The table below shows the top 10 pathogenic or likely-pathogenic variants currently classified in ClinVar for DHCR7.
View all on ClinVar →

Sample of pathogenic variants

10 pathogenic / likely-pathogenic variants from ClinVar, ranked by review status (expert-panel-reviewed first). This is a sample; recurrent founder variants in a specific population may not appear here - see the full ClinVar listing via the link above.

Variant (HGVS) Protein change Classification Evidence Associated condition
c.168C>A
single nucleotide variant
 p.Tyr56Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.187del
Deletion
 p.Gln63fs Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.359_374del
Deletion
 p.Lys120fs Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.369del
Deletion
 p.Gly124fs Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.375C>A
single nucleotide variant
 p.Tyr125Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.375C>G
single nucleotide variant
 p.Tyr125Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.445C>T
single nucleotide variant
 p.Gln149Ter Pathogenic/Likely pathogenic ★★☆☆ DHCR7-related disorder
c.651C>G
single nucleotide variant
 p.Tyr217Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.76C>T
single nucleotide variant
 p.Gln26Ter Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome
c.770C>G
single nucleotide variant
 p.Ala257Gly Pathogenic/Likely pathogenic ★★☆☆ Smith-Lemli-Opitz syndrome

Evidence stars indicate ClinVar review status. Individual variant interpretation should always be performed by a qualified clinical laboratory - many variants remain classified as Variants of Uncertain Significance (VUS) pending more research.

Associated conditions

Pathogenic variants in the DHCR7 gene are known to cause Smith-Lemli-Opitz syndrome. This condition is an autosomal recessive developmental disorder characterised by distinct facial features, microcephaly (small head size), and varying degrees of intellectual disability or learning difficulties. The severity and manifestation of Smith-Lemli-Opitz syndrome can differ significantly among affected individuals, depending on the specific genetic variants present.

  • Smith-Lemli-Opitz syndrome
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Inheritance pattern

Conditions caused by pathogenic DHCR7 variants typically follow autosomal recessive inheritance.

♀ Carrier parent 1 altered copy ♂ Carrier parent 1 altered copy Affected Carrier Carrier Unaffected Affected Carrier Unaffected Circles = females · Squares = males

When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.

Carrier frequency by population How common is heterozygous DHCR7 carrier status across ancestry groups?

UK clinical status

The DHCR7 gene is included in several NHS Genomic Medicine Service national test directories, reflecting its clinical significance within the UK. It is assessed for conditions such as Smith-Lemli-Opitz syndrome (R270), and in the investigation of likely inborn errors of metabolism (R98), foetal anomalies (R21), and intellectual disability. Additionally, DHCR7 is relevant for various ciliopathy-related disorders, including neurological, renal, and skeletal ciliopathies.

Green-listed
High evidence · clinically actionable in NHS testing
Included in NHS GMS signed-off panels
Bilateral congenital or childhood onset cataracts · R31 NHS GMS → Differences in sex development · R146 NHS GMS → Fetal anomalies · R21 NHS GMS → Holoprosencephaly · R85 NHS GMS → Likely inborn error of metabolism · R98 NHS GMS → Severe microcephaly · R88 NHS GMS → Skeletal dysplasia · R104 NHS GMS → Smith-Lemli-Opitz syndrome · R270 NHS GMS →
NHS Genomic Medicine Service Jeen carrier screening

Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory

Frequently asked questions

What is the primary function of the DHCR7 gene?

The DHCR7 gene provides instructions for making the enzyme 7-dehydrocholesterol reductase, which is responsible for the final step in the body's cholesterol production pathway, converting 7-dehydrocholesterol into cholesterol.

What condition is associated with DHCR7 gene variants?

Pathogenic variants in the DHCR7 gene are primarily associated with Smith-Lemli-Opitz syndrome, an autosomal recessive developmental disorder characterised by distinctive physical features, small head size, and intellectual challenges.

How is cholesterol important for the body?

Cholesterol has critical roles in the body, including aiding embryonic development, forming a structural component of cell membranes and nerve insulation (myelin), and serving as a precursor for hormones and bile acids essential for digestion.

References

  1. Bianconi SE, Cross JL, Wassif CA. Pathogenesis, Epidemiology, Diagnosis and Clinical Aspects of Smith-Lemli-Opitz Syndrome. Expert opinion on orphan drugs. 2015. PMID: 25734025
  2. Waterham HR, Hennekam RC. Mutational spectrum of Smith-Lemli-Opitz syndrome. American journal of medical genetics. Part C, Seminars in medical genetics. 2012. PMID: 23042628
  3. Tulenko TN, Boeze-Battaglia K, Mason RP. A membrane defect in the pathogenesis of the Smith-Lemli-Opitz syndrome. Journal of lipid research. 2006. PMID: 16258167
  4. Correa-Cerro LS, Porter FD. 3beta-hydroxysterol Delta7-reductase and the Smith-Lemli-Opitz syndrome. Molecular genetics and metabolism. 2005. PMID: 15670717
  5. Waye JS, Krakowiak PA, Wassif CA. Identification of nine novel DHCR7 missense mutations in patients with Smith-Lemli-Opitz syndrome (SLOS). Human mutation. 2005. PMID: 15954111
  6. Yu H, Patel SB. Recent insights into the Smith-Lemli-Opitz syndrome. Clinical genetics. 2005. PMID: 16207203
  7. Nowaczyk MJ, Martin-Garcia D, Aquino-Perna A. Founder effect for the T93M DHCR7 mutation in Smith-Lemli-Opitz syndrome. American journal of medical genetics. Part A. 2004. PMID: 14981719
  8. Jira PE, Waterham HR, Wanders RJ. Smith-Lemli-Opitz syndrome and the DHCR7 gene. Annals of human genetics. 2003. PMID: 12914579
  9. Nowaczyk MJ, Waye JS. The Smith-Lemli-Opitz syndrome: a novel metabolic way of understanding developmental biology, embryogenesis, and dysmorphology. Clinical genetics. 2001. PMID: 11453964
  10. Porter FD. RSH/Smith-Lemli-Opitz syndrome: a multiple congenital anomaly/mental retardation syndrome due to an inborn error of cholesterol biosynthesis. Molecular genetics and metabolism. 2000. PMID: 11001807
Educational content. This page is not medical or genetic advice, is not individually reviewed by a clinician for each reader, and should not replace a consultation with a qualified healthcare professional or genetic counsellor. If you are considering genetic testing or acting on a test result, book a consultation.
Data sources Last updated 18 October 2026. Content compiled from HGNC · MedlinePlus Genetics · ClinGen · Genomics England PanelApp · NHS National Genomic Test Directory · ClinVar · UniProt · AlphaFold .