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Blue Cone Monochromacy - Families

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Mari Molin updated their profile
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Renata left a comment for Heather McBryar
"Hi Heather, welcome ! I have just seen your email and I'm going to answer you about the Atlanta, GA Meeting. Thank you for joining us, Renata "
Jun 1
Profile IconHeather McBryar and Dean Edwards joined BCMfamilies
Jun 1
Renata left a comment for Dean Edwards
"Hi Dean, welcome ! This forum is about Blue Cone Monochromacy, a rare retinal disease. Please let me know if you want to receive BCM Families Foundation Newsletter. Kind Regards, Renata"
Jun 1
Renata replied to Renata's discussion Atlanta, GA (USA) – August 4-6th 2017 – BCM Families Meeting
"We have just sent OMNI Hotel confirmation numbers to all people who registered yet. If you registered and you didn't receive a confirmation number please write me at renata.sarno@bcmfamilies.org or info@bcmfamilies.org"
May 29
Renata replied to Renata's discussion Atlanta, GA (USA) – August 4-6th 2017 – BCM Families Meeting
"Dear BCM Families friends, I'm writing you about Atlanta, GA next 4-6th August meeting. Please don't wait last minute to register because we have only 7 hotel rooms available and only 12 seats in the meeting room. If you want to come…"
May 29
Renata replied to Renata's discussion Build our no profit organization
"Happy International Awareness Blue Cone Monochromacy Day  ! https://en.wikipedia.org/wiki/List_of_awareness_days#May"
May 21
Kay Johnson McCrary replied to Renata's discussion Build our no profit organization
"Happy third anniversary of becoming a nonprofit 501(c)(3)!  And Happy International BCM Day!!!"
May 21
Richard Weddle left a comment for Richard Weddle
"I completed genetic testing to confirm I have BCM with doctor Isnconne at Duke university last month. He suggested I register here with group. Yep I'd like to receive the newsletter."
May 21
Renata left a comment for Marylee Mohn
"I have 3 sons with BCM ! I understand you. Please write me at renata.sarno@bcmfamilies.org if you want more information and advice. Our ophthalmologist is Dr. S. Jacobson at Scheie Eye Institute, Philadelphia, PA, he is very expert on BCM.  In…"
May 21
Marylee Mohn left a comment for Renata
"Thanks for the FB and newsletter adds. We'll definitely get in touch with the University of Tubinga's lab about sending samples from my son and dad (and hopefully my cousins too.) I am supposed to work that weekend in August but will…"
May 21
Renata left a comment for Marylee Mohn
"Dear Marylee, thank you for joining us. I'm going to send you our last Newsletter and to add you to BCM group on facebook. Please consider the opportunity to come to Atlanta, GA next August 4-6th 2017. There will be the first international…"
May 21
Renata left a comment for Richard Weddle
"Hi Richard, Welcome ! This forum is about Blue Cone Monochromacy a rare retinal disease similar to achromatopsia. Please let me know if you want to receive our Newsletter and information about meetings, events, DNA test and Gene Therapy. Best…"
May 21
Richard Weddle is now a member of BCMfamilies
May 21
Marylee Mohn left a comment for Marylee Mohn
"Hi Renata, Thanks so much. My 9 month old son has nystagmus, and my dad and 2 of his nephews carried diagnoses of cone dystrophy. We are in the process of genetic testing on my dad after visiting Ocular Genetics at Wills Eye in Philly; Dr. Alex…"
May 15
Renata shared their discussion on Facebook
May 15
Renata posted a discussion

Atlanta, GA (USA) – August 4-6th 2017 – BCM Families Meeting

The first international meeting of families affected by Blue Cone Monochromacy will be in Atlanta, GA (USA) – on August 4-6th 2017Location will be OMNI Hotel Atlanta at CNN Center – Web Site – 100 CNN Center Atlanta, Georgia 30303 USA, Phone: (404) 659-0000 – Concierge: (404) 818-4406.Please visit…See More
May 14
Renata left a comment for Marylee Mohn
"Hi Marylee, Welcome ! This forum is about Blue Cone Monochromacy, a rare retinal disorder. Let me know whether you want to receive BCM Families Foundation's Newsletter. Please join BCM group on facebook Renata"
May 13
Marylee Mohn is now a member of BCMfamilies
May 13
Renata left a comment for Michelle
"Hi Michelle, Welcome ! This forum is about Blue Cone Monochromacy, a rare retinal disorder. Please join also BCM group on facebook. Renata"
May 12

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Build our no profit organization 18 Replies

Dear BCM families members,I found this linkhttp://www.rarediseases.org/patient-orgs/build-an-organd I'm thinking about the possibility to create ourown no-profit organization, what…Continue

Started by Renata in No Profit Organization for BCM. Last reply by Renata May 21.

Newsletter - summer 2015

Here you have our Summer 2015 Newsletter in english:…Continue

Started by Renata in No Profit Organization for BCM Aug 29, 2015.

Blue-Cone Monochromacy



Blue cone monochromatism is characterized by poor central vision and color discrimination, infantile nystagmus, and nearly normal retinal appearance. The psychophysiologic functions of both rods and blue cones are preserved (Lewis et al., 1987). The frequency of achromatopsia is said to be approximately 1 in 100,000 persons. The first detailed description is that given by Huddart (1777). The subject of that report 'could never do more than guess the name of any color; yet he could distinguish white from black, or black from any light or bright color...He had 2 brothers in the same circumstances as to sight; and 2 brothers and sisters who, as well as his parents, had nothing of this defect.' This disorder was previously interpreted as total colorblindness. Information presented by Spivey (1965) indicated that affected persons can see small blue objects on a large yellow field and vice versa. These cases have been variously called partial complete colorblindness, or incomplete achromatopsia. Blackwell and Blackwell (1961) have described achromatopic families in which a few blue cones seemed to be present. See comments of Alpern et al. (1960). Sloan (1964) also had evidence of the presence of a few red cones in cases of otherwise complete achromatopsia. Bromley (1974) showed me a large kindred with this disorder in a typical X-linked recessive pattern.

Lewis et al. (1987) showed linkage of blue cone monochromatism to 2 DNA markers (DXS15 and DXS52) that map in the Xq28 area. Southern blot analysis with clones derived from the red (303900) and green (303800) cone pigment genes showed loss or rearrangement of the cone pigment cluster, but in none of the 3 multigenerational families studied were all pigment genes missing. In all 12 families studied by Nathans et al. (1989), alterations were observed in the red and green visual pigment gene cluster. The alterations fell into 2 classes: one class arose from the wildtype by a 2-step pathway consisting of unequal homologous recombination and point mutation; the second class arose by nonhomologous deletion of genomic DNA adjacent to the red and green pigment gene cluster. These deletions defined a 579-bp region located 4 kb upstream of the red pigment gene and 43 kb upstream of the nearest green pigment gene; this region is essential for the activity of both pigment genes. Most persons with blue cone monochromacy have retinas that appear normal, but, in some, a progressive central retinal dystrophy is observed as they grow older. The dystrophic region corresponds to the fovea, the cone-rich area responsible for high acuity vision, and the immediately surrounding retina. Those individuals with the 2-step alteration presumably started out as dichromats in whom homologous unequal recombination had reduced to 1 the number of genes in the tandem array of cone pigment genes. This is a finding in approximately 1% of Caucasian X chromosomes. In the second step, a mutation inactivated the remaining gene; Nathans et al. (1989) found 2 examples of point mutations. Nathans et al. (1989) made an analogy to 2 forms of thalassemia in which absence of distant upstream sequences results in loss (in cis) of beta-globin gene expression. Within the deleted region are clusters of erythroid-specific deoxyribonuclease I 'hypersensitivity' sites. It has been found in transgenic mice that fragments from these sites confer on a linked human beta-globin gene uniformly high, tissue-specific expression independent of chromosomal position. These observations support a model in which distant sequences act to coordinate tissue-specific gene expression. The fact that 1 patient developed a slowly progressive central retinal dystrophy suggested to Nathans et al. (1989) that, by analogy, some peripheral retinal dystrophies may be caused by mutations in the genes encoding rhodopsin or other rod proteins.

Nathans et al. (1993) examined the tandem array of red and green cone pigment genes on the X chromosome. In 24 subjects, 8 genotypes were found that would be predicted to eliminate the function of all of the genes within the array. As observed in an earlier study, the rearrangements involved either deletion of a locus control region adjacent to the gene array or loss of function via homologous recombination and point mutation. In 15 probands who carried a single gene, an inactivating mutation, cys203 to arg (303800.0001), was found, and both visual pigment genes carried the mutation in 1 subject whose array had 2 genes. This mutation was also found in at least one of the visual pigment genes in 1 subject whose array had multiple genes and in 2 of 321 control subjects, suggesting that preexisting cys203-to-arg mutations constitute a reservoir of chromosomes that are predisposed to generate blue-cone-monochromat genotypes by unequal homologous recombination and/or gene conversion. Two other point mutations were identified: arg247 to ter in a subject with a single red-pigment gene, and pro307 to leu in a subject with a single 5-prime-red/3-prime-green hybrid gene. The observed heterogeneity of genotypes pointed to the existence of multiple 1- and 2-step mutational pathways to blue cone monochromacy.

Nathans et al. (1993) stated that 6 different deletions, ranging in size from 0.6 kb to 55 kb, had been found in, or adjacent to, otherwise typical red-green pigment gene arrays. All of these deletions encompassed a common region between 3.1 kb and 3.7 kb 5-prime of the array. Wang et al. (1992) reported the results of experiments in which sequences 5-prime of the red- and green-pigment array directed expression of a beta-galactosidase reporter gene in transgenic mice, indicating that the region between 3.1 kb and 3.7 kb 5-prime of the array functions as an essential activator of cone-specific gene expression. The existence of a form of blue cone monochromacy due to a change in the genome removed from the color vision genes themselves justifies the inclusion of an asterisked entry distinct from the entries for the CBD (GCP, 303800) and CBP (RCP, 303900) genes.
 
 
 

Blue Cone Monochromatism is a rare genetic disease. Red and green opsin genes OPN1L OPN1M. Xq28.

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