BEST2

BEST2 belongs to the bestrophin family of anion channels — proteins that form tiny pores allowing negatively charged particles to pass through a cell's outer membrane. Laboratory work has shown that bestrophin channels, including bestrophin-2, can carry chloride and are also highly permeable to bicarbonate. According to the reference gene record, BEST2 is mainly active in the colon and was originally described in the retinal pigment epithelium, the support layer beneath the retina. However, when researchers examined human donor eyes directly, they could not detect bestrophin-2 in the retinal pigment epithelium and instead found it in the non-pigmented ciliary epithelium. This is an important distinction, because it points away from a direct role in the retina itself.

The human and animal evidence gathered here connects bestrophin-2 to the fluid dynamics and pressure of the eye rather than to the breakdown of light-sensing cells. In mice bred without a working BEST2 gene, the flow and drainage of fluid inside the eye changed, resulting in lower pressure inside the eye compared with normal mice. Because of this, researchers have described bestrophin-2 as a possible target for glaucoma therapy, a separate condition driven by eye pressure — not as a cause of retinal degeneration. None of the reviewed records describe BEST2 variants producing the progressive loss of night vision or peripheral vision seen in retinitis pigmentosa.

Bestrophin-2 is one of four bestrophin proteins in humans, and its overall structure and chemistry are well studied in the laboratory. Detailed molecular structures show that bestrophin-2 can bind the signaling chemicals glutamate and GABA, and that it partners with an enzyme called glutamine synthetase in the ciliary body to help release glutamate. Its location in the non-pigmented ciliary epithelium of the human eye is supported by direct protein studies of donor tissue. By contrast, the related gene BEST1 has more than 200 known disease-causing variants and is firmly linked to several inherited eye conditions, most notably Best vitelliform macular dystrophy.

The precise physiological job of bestrophin-2 in the eye remains debated, including whether it acts mainly as a chloride channel or in another role. Studies in mice showed that fluid behavior in the eye did not fit a simple chloride-channel explanation, which led researchers to call for the assumed function of the bestrophins to be reassessed. Most importantly for anyone who has received a BEST2 result, the reviewed evidence does not establish that changes in this gene cause inherited retinal disease in people. If a laboratory report has listed BEST2 in connection with retinitis pigmentosa, that association is disputed and is not supported by the evidence collected here.

As of the date of this review, no treatment targeting BEST2 has been approved, and the reviewed records do not identify a gene-specific therapy. Most research on bestrophin-2 is laboratory or animal work aimed at understanding how the channel is built and controlled. In one recent laboratory study, scientists mapped drug-binding sites on bestrophin channels and found that a small molecule called PABA (4-aminobenzoic acid) could restore function to certain BEST1 mutations in cells. That finding concerns BEST1, not BEST2, and was carried out in cells rather than in people, so it is not an available treatment. Because bestrophin-2 influences eye-pressure biology, some researchers have discussed it as a possible future target for glaucoma, which is a separate line of inquiry from inherited retinal disease.

• Bestrophin-2 is found in the ciliary body, not the retina, in human eyes

  Laboratory study of human donor tissue

  What was found:

  Bestrophin-2 could not be detected in the retinal pigment epithelium; instead it was found in non-pigmented ciliary epithelial cells, which help regulate eye fluid and pressure.

  Why it matters:

  This directly argues against BEST2 acting in the retina and points to a role in eye-pressure biology rather than retinal degeneration.

  Limitation: The protein was only detectable after enrichment, and the study examined location, not disease causation.

• Best2-deficient mice show altered eye pressure

  Animal (mouse) study

  What was found:

  Mice without Best2 had lower intraocular pressure despite producing more eye fluid, linking the protein to pressure regulation in the ciliary body.

  Why it matters:

  It supports a role for bestrophin-2 in eye-pressure biology, a different mechanism from inherited retinal disease.

  Limitation: Mouse eye biology may differ from humans, and the work does not address retinal degeneration.

• Structure of bestrophin-2 paired with glutamine synthetase

  Laboratory structural and cell study

  What was found:

  Bestrophin-2 can release glutamate and is regulated by its enzyme partner in non-pigmented ciliary epithelial cells.

  Why it matters:

  It deepens understanding of bestrophin-2's normal chemistry in the ciliary body.

  Limitation: This is basic mechanism research and does not connect the gene to any human retinal disease.

• Small molecules that activate bestrophin channels

  Laboratory (cell and structural) study

  What was found:

  PABA rescued the function of certain disease-causing BEST1 mutations in patient-derived cells and activated bestrophin channels at newly identified sites.

  Why it matters:

  It highlights possible future drug directions for bestrophin-related conditions, chiefly those tied to BEST1.

  Limitation: The rescue involved BEST1, not BEST2, and was performed in cells, so it is not an available or gene-specific treatment.

• Review of bestrophin function questions the assumed channel role

  Peer-reviewed review

  What was found:

  Findings from knockout mice and a newly discovered recessive bestrophinopathy suggested the bestrophins' presumed chloride-channel function needed to be reassessed, and Best2 did not behave as a simple chloride channel in the eye.

  Why it matters:

  It shows genuine scientific uncertainty about what bestrophin-2 does and cautions against assuming a fixed disease role.

  Limitation: A review summarizes other work and does not itself generate new patient data.

This gene does not raise distinct family or caregiver considerations beyond the general guidance shown on every gene page.

• Does my BEST2 result explain my eye symptoms, or should other genes be considered?
• Was this variant classified as disease-causing, uncertain, or benign in my report?
• Could my result reflect a change in the related gene BEST1 rather than BEST2?
• Would additional or repeat genetic testing help clarify the cause of my diagnosis?
• Are there any eye-pressure or ciliary-body findings in my exam that relate to bestrophin-2?
• Would seeing a genetic counselor help interpret what this result means for me and my family?

If a genetic test has flagged a change in BEST2, it may be helpful to review with a retinal specialist or genetic counselor whether this finding actually explains any vision symptoms. Because the evidence does not connect BEST2 to retinal degeneration, it may be worth asking whether another gene could better account for the diagnosis. You can also use RP Hope's Clinical Trials Finder to explore current research, keeping in mind that no BEST2-specific trials were found in this review.