Friday, September 26, 2008

dHPLC and automated DNA sequencing were used to detect the paternally inherited fetal mutation in a maternal plasma sample collected at the 12th week

Early noninvasive prenatal detection of a fetal CRB1 mutation causing Leber congenital amaurosis.Bustamante-Aragones A, Vallespin E, Rodriguez de Alba M, Trujillo-Tiebas MJ, Gonzalez-Gonzalez C, Diego-Alvarez D, Riveiro-Alvarez R, Lorda-Sanchez I, Ayuso C, Ramos C.
Department of Genetics, Fundacion Jimenez Diaz-Capio, CIBERER, Madrid, Spain.

PURPOSE: Leber congenital amaurosis (LCA) is one of the most severe inherited retinal dystrophies with the earliest age of onset. Mutations in the Crumbs homologue 1 (CRB1; OMIM 600105) gene explain 10%-24% of cases with LCA depending on the population. The aim of the present work was to study a fetal mutation associated to LCA in maternal plasma by a new methodology in the noninvasive prenatal diagnosis field: the denaturing High Performance Liquid Chromatography (dHPLC). METHODS: This study presents the case of a compound heterozygous fetus for two mutations in CRB1 (1q3.1-q32.2). dHPLC and automated DNA sequencing were used to detect the paternally inherited fetal mutation in a maternal plasma sample collected at the 12th week of gestation. To test the detection limit of dHPLC, we made serial dilutions of paternal DNA in control DNA. RESULTS: We were able to detect the presence of the paternally inherited fetal CRB1 mutation in maternal plasma by dHPLC. Moreover, by comparing chromatograms of serial dilutions to the plasma sample, we could ascertain that the percentage of fetal DNA in maternal plasma was at least 2%. However, the detection of the fetal mutation was not possible by automated DNA sequencing. CONCLUSIONS: dHPLC seems to be sensitive enough to detect small amounts of fetal DNA in maternal plasma samples. It could be a useful tool for the noninvasive prenatal detection of paternally inherited point mutations associated with retinopathies.


Sunday, September 14, 2008

Achondroplasia a function of paternal ageing

1: Am J Med Genet A. 2008 Sep 15;146A(18):2385-9. Links
The population-based prevalence of achondroplasia and thanatophoric dysplasia in selected regions of the US.Waller DK, Correa A, Vo TM, Wang Y, Hobbs C, Langlois PH, Pearson K, Romitti PA, Shaw GM, Hecht JT.
Houston Health Science Center, The University of Texas, Houston, Texas 77030, USA.

There have been no large population-based studies of the prevalence of achondroplasia and thanatophroic dysplasia in the United States. This study compared data from seven population-based birth defects monitoring programs in the United States. We also present data on the association between older paternal age and these birth defects, which has been described in earlier studies. The prevalence of achondroplasia ranged from 0.36 to 0.60 per 10,000 livebirths (1/27,780-1/16,670 livebirths). The prevalence of thanatophoric dysplasia ranged from 0.21 to 0.30 per 10,000 livebirths (1/33,330-1/47,620 livebirths). In Texas, fathers that were 25-29, 30-34, 35-39, and > or =40 years of age had significantly increased rates of de novo achondroplasia among their offspring compared with younger fathers. The adjusted prevalence odds ratios were 2.8 (95% CI; 1.2, 6.7), 2.8 (95% CI; 1.0, 7.6), 4.9 (95% CI; 1.7, 14.3), and 5.0 (95% CI; 1.5, 16.1), respectively. Using the same age categories, the crude prevalence odds ratios for de novo cases of thanatophoric dysplasia in Texas were 5.8 (95% CI; 1.7, 9.8), 3.9 (95% CI; 1.1, 6.7), 6.1 (95% CI; 1.6, 10.6), and 10.2 (95% CI; 2.6, 17.8), respectively. These data suggest that thanatophoric dysplasia is one-third to one-half as frequent as achondroplasia. The differences in the prevalence of these conditions across monitoring programs were consistent with random fluctuation. Birth defects monitoring programs may be a good source of ascertainment for population-based studies of achondroplasia and thanatophoric dysplasia, provided that diagnoses are confirmed by review of medical records. Copyright 2008 Wiley-Liss, Inc.

PMID: 18698630 [PubMed - indexed for MEDLINE]


Wednesday, September 10, 2008

Change in Single Gene Causes Degenerative Brain Disease in Mice

September 10, 2008
Change in Single Gene Causes Degenerative Brain Disease in Mice

Mice whose brains receive half the dose of a critical growth-regulating gene exhibit the altered behaviors and nerve cell tangles common in people with Alzheimer's disease or dementia, according to a new report by Howard Hughes Medical Institute (HHMI) scientists.

The study, led by HHMI international research scholar Freda Miller, shows that changing just one copy of the p73 gene threw off the balance between cellular life and death in the brain.

“The big shock was that half the level of just one gene had such a big impact.”
Freda D. Miller

“The big shock was that half the level of just one gene had such a big impact,” explains Miller, who is at the Hospital for Sick Children in Toronto. Finding a single protein with such a large impact on anatomy and behavior is an important step toward understanding and treating neurodegenerative diseases.

Miller and David Kaplan at the University of Toronto led the research team, which reports their finding in the September 11, 2008, issue of the journal Neuron.

As the brain develops, neural cells and connections that are no longer needed are pruned away. A number of different molecules determine when to kill off nerve cells that are damaged or no longer needed. To balance the molecules that bring about cell death, other molecules, like the p73 protein, play an “anti-death role” in the brain, Miller's team reported in a Science paper in 2000. “There are a number of checkpoints to keep cells from writing themselves off,” she says.

More recent investigations found that some patients with Alzheimer's disease naturally lack one copy of the p73 gene, and likely have lower p73 protein levels as a result. Those findings did not necessarily mean that lower levels of p73 contribute to Alzheimer's, but they strongly suggested that the protein may protect healthy individuals.

Looking for a more definitive answer, Miller's team studied genetically engineered mice that were born with only one copy of the p73 gene. The mice lacking one copy of p73 behaved differently than normal mice, and the differences increased as they grew older. For example, Miller's team found that mice with reduced p73 took longer to find their way out of a water maze than normal mice. They also displayed an unusual behavior clasping their legs together when held up by their tails. “Instead of splaying their legs out, they clasped them into their bodies,” Miller says. “My postdoc came and said, `Freda, these mice are acting very strangely.'”

Miller's team then searched for anatomical evidence that the reduction in p73 was affecting the brains of the mice. Using magnetic resonance imaging, the researchers found that the motor cortex and several other regions of the brain had 5-16 percent less volume than the same areas in healthy mice.

Later, when they dissected the brains, they found accumulations of Alzheimer's-related tangles inside and outside cells, composed mostly of a nervous system protein called tau that incorrectly attached to phosphate molecules. “Accumulation of the aberrant form of tau and tangles is bad for your brain,” Miller says.

It is still unclear how these accumulations harm the brain, but they are common in patients with neurodegenerative diseases. P73 may indirectly regulate the formation of tangles in its role as an anti-death cell monitor.

Miller's next step is to see if reductions in p73 have the same impact in humans. The team will look for changes in the number of copies of the p73 sequence in a larger population and see whether a reduced amount of p73 is more common in people with neurodegenerative disorders than in the healthy population, Miller says.

“The good news is this isn't a situation where people are completely missing this gene,” Miller says. The people already found to have variations in P73 genes tend to have some p73 production capacity, which might be exploited and improved with drugs. For instance, “we already know that growth factors really increase levels of the normal, pro-life version of p73.”

The mixture of molecules required to sustain our nerve cells for a human lifespan is so complicated, that “it's a miracle that as we get older we can think at all,” she jokes. People missing one copy of p73 will not necessarily suffer from degeneration of their brains, Miller says, but, “we think of it as a susceptibility factor for neurodegeneration or injury.”


Tuesday, September 9, 2008

What about sporadic retinoblastoma?

Familial Retinoblastoma With Unilateral and Unifocal Involvement in 2 Families
Shaden Sarafzadeh, MD; Zélia M. Corrêa, MD, PhD; James J. Augsburger, MD

Arch Ophthalmol. 2008;126(9):1308-1309.

Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

Retinoblastoma is a malignant ocular tumor of childhood that occurs in approximately 1 in 18 000 children.1 Approximately 40% of patients with retinoblastoma have inherited a germ-line mutation of the RB1 gene (gene map locus 13q14.1-q14.2) (OMIN+180200), and approximately 85% of them develop bilateral tumors.2 We report on the cases of 2 children from 2 different families; all 4 of these children developed unilateral unifocal retinoblastoma despite no family history of retinoblastoma.


This is a retrospective report of 2 families without a history of retinoblastoma in which both children in each family developed unifocal unilateral retinoblastoma.

Two sets of siblings (n = 4) developed unifocal unilateral retinoblastoma and neither family had a history of retinoblastoma. The first affected sibling in each family was male and received his diagnosis at age 11 months in family 1 and at age 10 . . . [Full Text of this Article]

Family 1

Family 2




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