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Genetic Factors for Leber Congenital Amaurosis (LCA)

Introduction
ABC News Nightline recently aired a story about six-year-old Monroe, twenty-five-year-old Heather and then twelve-year old Christian who all suffered from a severe ocular impairment disease called Leber Congenital Amaurosis or LCA. This rare disease causes retinal dystrophy and is inherited. The eye disorder causes severe vision loss at birth, or within the first few years of life, and is the common cause of all inherited childhood blindness cases.
According to studies done at University of California San Francisco Health, “LCA affects both the peripheral rod cells, which allow you to see at night, and the central cone cells, responsible for fine detail and color vision.” (University of California San Francisco Health, n.d., para. 1). All three subjects in the Nightline dossier could not see anything at night and needed assistance to see clearly during the day, but as drug-trial subjects, could now improve vision due to the type of LCA they have.
There are at least thirteen variations of LCA distinguishable by cause, eye abnormalities and severity of loss of vision. Because LCA can result from mutations of 14 or more genes that have several pertinent roles in the function, development of the retina, and normal vision, these variations of the disease occur. (“Genetics Home Reference: Your Guide to Understanding Genetic Conditions,” Reviewed August 2010, Published July16, 2019, Causes p. 1).
Patients that suffer from one of two mutations of the RPE65 gene, have an opportunity to improve the affects of LCA through new breakthroughs in gene therapy. Mutations of the RPE65 gene are linked to approximately 6% of LCA diagnoses. (University of California San Francisco Health, n.d., Treatment Tab)
I. Cause. A genetic mutation, inheritance of a recessive or dominate gene?
LCA is commonly inherited through families by autosomal recessive genes. Confirmation of genetic heterogeneity was done in 1995 when the disease-causing gene was linked to chromosome 17p13. By 1996, LCA1 mutations we discovered in the photoreceptor-specific guanylate cyclase gene (retGC1), an essential protein for phototransduction (ability for eyes to recover in the dark). Mutations in a specific retinal pigment epithelium gene (RPE65) was discovered in 1997. (Perrault et al., Received 2 July 1999, Revised 21 July 1999, Available online 25 May 2002.).
The protein RPE65 (LCA2) metabolizes vitamin A; failures in this process are link to 5% of all retinal dystrophies and up to 18% of congenital blindness. Symptoms of LCA are poor visual function, usually with nystagmus (involuntary eye movement), nyctalopia (night blindness), photophobia (light sensitivity), diminished electroretinogram, high hyperopia (farsightedness), keratoconus (coning corneas), abnormal pupillary responses and occasionally, Franceschetti’s oculo-digital indicating eye poking, pressing, and rubbing.” (“Blueprint Genetics / Tests / Panels / Ophthalmology / Leber Congenital Amaurosis,” 2019).

This table was compiled from database called the Human Phenotype Ontology (HPO). HPO collects information on symptoms that have been described in medical resources. (Genetic and Rare Diseases Information Center (GARD), n.d., Symptoms Table 1)
II. Trait in families. Passing genes to children. Prevalence male/female.
Risks for children to have this recessive gene disorder increases with parents who are close relatives (consanguineous) as they have a higher chance than unrelated parents to each carry the same abnormal gene. Since both parents must carry a defective gene to pass LCA on to their children, offspring have a 25% chance of inheriting two LCA genes (one from each parent). Both male and female offspring share equal risks of inheriting the disorder from the parents. (National Organization for Rare Disorders (NORD), 1986, 1987, 1990, 1996, 1997, 2001, 2010, 2017), (University of California San Francisco Health, n.d.), (https://www.ucsfhealth.org/conditions/leber_congenital_amaurosis/).
III. Dominant or Recessive-Autosomal or Sex-linked or a Mitochondrial disorder
Leber congenital amaurosis is typically an autosomal recessive gene disorder, but some autosomal dominant inheritance cases have been recording. According to a March 2002 article from Human Molecular Genetics:
“Since 1996, six genes involved in LCA have been identified, that is, aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) (6), Crumbs homolog 1 (CRB1) (7,8), cone–rod homeobox (CRX) (9), guanylate cyclase 2D (GUCY2D, RETGC1) (10), RPE65 (11), and retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) (12). In addition, linkage studies have revealed LCA loci on 14q24 (LCA3) (13) and 6q11-q16 (LCA5) (14). Other genes that have been associated with early-onset retinal dystrophy, including LRAT, MERTK, PROML1, and TULP1, are not considered LCA genes since the associated phenotypes are typical of juvenile or early-onset retinitis pigmentosa (RP) rather than LCA (15–18).” (Cremers, Van den Hurk,

Medical Uses of Ayahuasca

Many plants, from many different families, have been shown to contain valuable chemical properties that humans have utilized medicinally for centuries. Traditional medicine systems relied on these plant properties to treat physical, mental, and spiritual injury. Specialists within a community had knowledge of which plants would effectively treat or sooth which ailments. In ancient cultures, medical practice and religion were often intertwined. Many people attributed illness to supernatural forces or to an imbalance between the universe and the body, mind, or spirit. Therefore, indigenous peoples viewed spiritual health to be just as important as physical health. The indigenous tribes of the Upper Amazon, (more specifically the tribes that occupy the northwestern region of the Amazon Basin where Colombia, Peru, Ecuador, and Brazil come together), have a long history of utilizing plants for ritualistic purposes. One such supplement used by almost 100% of the tribes in this area is Ayahuasca (Sachahambi, 2008). Ayahuasca is a mixture consisting of Banisteriopsis caapi vine with the leaves of Psychotria viridis, these two components are boiled together into a tea which is then consumed for medicinal purposes, often used to make contact with supernatural realms to aid in spiritual healing. Both of these plant species contain psychoactive compounds that cause the consumer to experience auditory and visual hallucinations. This paper starts with a discussion of the two plant species used in the preparation of ayahuasca and how the combination of the two work together to produce the observed effects in humans. In addition, we will look at the potential use of ayahuasca for therapeutic purposes, and what role it may play in future medicine.
Banisteriopsis caapi is a vine of the Malpighiaceae family, preferring a moist tropical environment (Morton, C.V.). The plant is a large climbing shrub, with woody stems that can reach up to thirty meters in length, supporting itself by twining around neighboring plants or trees. Its natural range includes much of northern and western South America. The bark of the vine contains several β-carboline alkaloids, primarily harmine and tetrahydroharmine (THH) with lesser amounts of harmaline (Riba et al., 2003). These alkaloids are reversible monoamine-oxidase-A inhibitors (MAO-AI). MAO-AIs work to prevent the breakdown of serotonin and norepinephrine, which allows the levels of these molecules to increase in the brain, thus many antidepressants act as MAO inhibitors, working to restore mental balance in individuals with low levels of serotonin (Antidepressant Agents, 11:40-11:55). In 2010, Samoylenko et al., confirmed that B.caapi contained two antioxidant flavanols, epicatechin and procyanidin B2. These proanthocyanidins together with harmine and harmaline (-carboline alkaloids) inhibit monoamine oxidase B (MAO-B) (Samoylenko et al., 2010). Recent literature suggests that the previously mentioned active compounds present in B. caapi contribute to neurogenesis, improved memory/learning function, and increased dopamine secretion (Dos Santos

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