CWC27

The CWC27 gene carries instructions for a protein called a spliceosome-associated cyclophilin. This protein takes part in pre-mRNA splicing, a step in which the cell edits genetic messages so that proteins can be built correctly. Researchers have shown, in laboratory and animal studies, that CWC27 works together with a partner protein called CWC22 and helps assemble part of the splicing machinery. CWC27-related disease is inherited in an autosomal recessive (definition: An inheritance pattern where a person needs an altered copy of a gene from both parents to be affected. Parents with only one copy are usually unaffected carriers.) pattern, meaning a person is typically affected only when they inherit a disease-causing variant from each parent. It is important to understand that this gene is linked to a broader condition in which retinal degeneration is one feature — not only an eye disease. Because splicing is used throughout the body, variants in CWC27 can affect several organ systems, though how much they are affected differs greatly between individuals.

In the people described in the available reports, CWC27-related disease commonly affects the retina, the light-sensing tissue at the back of the eye. Reported eye symptoms have included poor vision, night blindness (nyctalopia), and involuntary eye movements (nystagmus) beginning in childhood. Detailed eye examinations in one reported patient showed widespread chorioretinal atrophy with scattered pigment changes and areas of macular atrophy, along with thinning of the retina on imaging. The retinal condition has been described using terms such as retinitis pigmentosa and retinal degeneration, and it can occur either in isolation or together with other body-wide features. Age of onset, severity, and rate of change vary from person to person, so these reports describe what has been seen in a small number of patients rather than a fixed course for any individual.

It is established that harmful variants affecting both copies of CWC27 can cause a recessive disorder that includes retinal degeneration. The original report that linked CWC27 to human disease identified protein-truncating variants in seven unrelated families with phenotypes ranging from isolated retinitis pigmentosa to severe syndromic forms. Beyond the eyes, described features across multiple reports have included short stature, brachydactyly (short fingers), craniofacial (face and skull) differences, dental anomalies, and neurological defects. Later case reports have expanded the recognized picture to include additional findings such as sparse hair, thin eyebrows and eyelashes, pigmentary (skin color) differences, nail changes, and, in individual patients, features like cataracts or thyroid and kidney findings. This condition is rare; at the time of one 2024 report only 14 patients had been described in the medical literature, and it has been found in patients from several different populations. Laboratory and animal studies confirm that CWC27 acts as a splicing factor and that its loss disrupts splicing and gene activity in the retina.

Because so few patients have been reported, the full range of symptoms and how the condition changes over time are still being defined. It is not fully understood why some people with CWC27 variants have mainly eye disease while others have extensive syndromic features — this variability in expression has been observed but not fully explained. How a specific variant relates to a specific outcome (genotype (definition: A person's specific genetic makeup — which gene and which variant is causing their condition — as opposed to the phenotype, the symptoms it produces.)–phenotype (definition: The observable traits or symptoms a condition actually produces in a person — as opposed to the genotype, the underlying genetic cause.) correlation) is not yet clear from the small number of cases. A possible role of CWC27 in inner-ear development and hearing has been studied only in mice, so its relevance to people is not established. Mentions of Cwc27 in relation to Alzheimer's disease come from studies of circular RNA and do not establish a link between this gene and dementia in patients with CWC27-related retinal disease.

RP Hope's reviewed records do not currently identify a gene-specific approved treatment for CWC27-related disease. One case report noted that no specific drug was available and that supportive care such as rehabilitation training was used. In laboratory research, scientists have used mouse models to study how loss of CWC27 damages photoreceptors and disrupts splicing in the retina. A preclinical (definition: Research done in cells or animals, before a treatment is considered ready to be studied in people.) study reported that delivering a working copy of CWC27 into the eye of mutant mice using an AAV gene-therapy vector improved retinal function and structure and reduced photoreceptor (definition: A light-sensing cell in the retina. Rods (used for night and peripheral vision) and cones (used for color and detail) are the two types.) loss. This gene-therapy work was done only in mice and is not an available treatment for people; it represents an early research direction, not a therapy that has been tested for safety or benefit in humans.

• Discovery that CWC27 variants cause retinal degeneration with or without syndromic features

  Human genetic study with supporting animal models.

  What was found:

  Recessive protein-truncating CWC27 variants caused a spectrum ranging from isolated retinitis pigmentosa to severe syndromic disease with brachydactyly, craniofacial abnormalities, short stature, and neurological defects; mice reproduced this variable severity.

  Why it matters:

  This is the foundational study establishing CWC27 as a disease gene and showing that the same gene can cause either eye-limited or broader syndromic disease.

  Limitation: Based on a small number of families, so the full range and frequency of features remain uncertain.

• Evidence that CWC27 acts as a splicing factor in the retina

  Animal and laboratory research.

  What was found:

  Loss of Cwc27 changed splicing patterns and gene activity in the retina and appeared to trigger cellular (ER) stress, offering clues to how the disease damages photoreceptors.

  Why it matters:

  Understanding the disease mechanism is a step toward developing targeted therapies.

  Limitation: Findings are from mice and cells, not patients, and describe mechanism rather than treatment.

• Gene-therapy proof-of-concept in mutant mice

  Preclinical animal study.

  What was found:

  Treated eyes showed improved retinal function and structure and less photoreceptor (including cone) loss compared with untreated eyes.

  Why it matters:

  It suggests gene replacement is a promising research direction for CWC27-related retinal degeneration.

  Limitation: Performed only in mice; this is not an available or human-tested treatment.

• A novel CWC27 deletion in a patient with early-onset RP and syndromic features

  Single case report.

  What was found:

  The patient had childhood-onset poor vision, night blindness, and nystagmus with extensive chorioretinal and macular atrophy, alongside craniofacial abnormalities, short stature, brachydactyly, dental anomalies, café-au-lait spots, and sparse hair; a novel homozygous deletion was identified.

  Why it matters:

  It illustrates the combined eye and body-wide features and broadens the known set of disease-causing variants.

  Limitation: One patient only; individual findings cannot be generalized to everyone with a CWC27 variant.

• Case report and literature review further defining the syndrome

  Case report with literature review.

  What was found:

  The siblings showed ocular and non-ocular features including novel findings such as a solitary kidney and Hashimoto's thyroiditis, and the review highlighted ectodermal features (sparse hair, eyebrow/eyelash thinning, pigmentary and nail changes, dental anomalies) as a core part of the condition.

  Why it matters:

  It helps clinicians recognize the wider pattern of features beyond the retina.

  Limitation: Small number of individuals; some features were seen in only one person.

CWC27-related disease is inherited recessively, so family members with questions about their own status may find genetic counseling useful. A supportive approach starts with asking the person what kind of assistance, if any, they would prefer, rather than assuming help is needed for every task. Low-vision rehabilitation and accessible technology can support independence for people living with retinal degeneration. Because the condition can affect areas such as growth, teeth, the skeleton, or development in some individuals, coordinating care across specialists may ease day-to-day support. Reading first-person accounts from other patients and families can offer emotional and community support during a new diagnosis. RP Hope's My RP Pathway can help families find relevant resources at whatever stage they are in.

• Does my (or my child's) CWC27 result appear to be isolated retinal disease, or is a broader syndrome evaluation recommended?
• Which other specialists — for example in bone/skeletal, dental, neurological, or hearing concerns — might be helpful to involve?
• What eye tests would help track the retinal changes over time?
• What is known about the specific CWC27 variant identified in our family?
• What does an autosomal recessive result mean for other family members who may want genetic counseling?
• Are there low-vision or rehabilitation services you would recommend now?

Because CWC27-related disease can involve more than the eyes, it may be helpful to discuss with your care team whether evaluation of other body systems is appropriate. Confirming a genetic diagnosis with a specialist and a genetic counselor can help clarify what a CWC27 result means for you and your family. RP Hope's genetic testing resource explains why testing matters, what it involves, and questions to ask a genetic counselor. A guided tour of RP Hope's resources for patients and families at any stage is available through My RP Pathway. To explore whether any studies might be relevant, you can use RP Hope's Clinical Trials Finder, where CWC27 can be preselected, rather than trying to judge eligibility on your own.