GGCX mutations in a patient with overlapping pseudoxanthoma elasticum/cutis laxa-like phenotype.

Pseudoxanthoma elasticum (PXE) is a multisystem disorder characterized by ectopic mineralization of connective tissues with primary manifestations in the skin, eyes and the cardiovascular system. The classic forms of PXE are caused by mutations in the ABCC6 gene encoding the ABCC6 protein, expressed primarily in the liver. Cutis laxa (CL) manifests with loose and sagging skin with loss of recoil. In 2009 we investigated a 19-year-old patient with overlapping cutaneous features of PXE and CL, together with alpha thalassaemia. Genetic analysis failed to identify pathogenic mutations in ABCC6. More recently we developed a gene-targeted panel of next-generation sequencing technology. This panel has 29 genes, 22 of which, including ABCC6 and GGCX, are associated with ectopic mineralization phenotypes. Mutation analysis in the patient identified two heterozygous GGCX mutations: c.200_201delTT in exon 2 and c.763G>A, p.V255M in exon 7. The GGCX gene encodes a γ-glutamyl carboxylase necessary for activation of blood coagulation factors in the liver. The p.V255M mutation was previously reported to result in reduced γ-glutamyl carboxylase activity in vitro, while the c.200_201delTT mutation is novel. Previous studies reported that mutations in GGCX cause overlapping PXE/CL skin phenotypes in association with or without multiple vitamin K-dependent coagulation factor deficiency. Our patient had loose redundant skin, moderate-to-severe angioid streaks and characteristic calcification of elastic structures in the mid dermis, consistent with PXE/CL overlap, but no coagulation abnormalities. Our studies expand the GGCX mutation landscape in patients with PXE-like phenotypes.

How will GINA influence participation in pharmacogenomics research and clinical testing?

After a 13-year battle in Congress--longer than it took to map the human genome--the Genetic Information Nondiscrimination Act (GINA) was passed into law on 21 May 2008. Before its passing, Francis Collins, then director of the National Human Genome Research Institute, testified before the 110th Congress that the success of personalized medicine hinged on the passing of the legislation. How will GINA, which takes effect in 2009, influence participation in pharmacogenomic research and clinical testing?

A spectrum of ABCC6 mutations is responsible for pseudoxanthoma elasticum.

To better understand the pathogenetics of pseudoxanthoma elasticum (PXE), we performed a mutational analysis of ATP-binding cassette subfamily C member 6 (ABCC6) in 122 unrelated patients with PXE, the largest cohort of patients yet studied. Thirty-six mutations were characterized, and, among these, 28 were novel variants (for a total of 43 PXE mutations known to date). Twenty-one alleles were missense variants, six were small insertions or deletions, five were nonsense, two were alleles likely to result in aberrant mRNA splicing, and two were large deletions involving ABCC6. Although most mutations appeared to be unique variants, two disease-causing alleles occurred frequently in apparently unrelated individuals. R1141X was found in our patient cohort at a frequency of 18.8% and was preponderant in European patients. ABCC6del23-29 occurred at a frequency of 12.9% and was prevalent in patients from the United States. These results suggested that R1141X and ABCC6del23-29 might have been derived regionally from founder alleles. Putative disease-causing mutations were identified in approximately 64% of the 244 chromosomes studied, and 85.2% of the 122 patients were found to have at least one disease-causing allele. Our results suggest that a fraction of the undetected mutant alleles could be either genomic rearrangements or mutations occurring in noncoding regions of the ABCC6 gene. The distribution pattern of ABCC6 mutations revealed a cluster of disease-causing variants within exons encoding a large C-terminal cytoplasmic loop and in the C-terminal nucleotide-binding domain (NBD2). We discuss the potential structural and functional significance of this mutation pattern within the context of the complex relationship between the PXE phenotype and the function of ABCC6.

Researching the biology of PXE: partnering in the process.

PXE International, a disease advocacy group, plays a central role as a catalyst in several research initiatives focused on the biology, epidemiology, and genetics of pseudoxanthoma elasticum (PXE). These initiatives accelerate research on PXE and provide a basis for several productive collaborative partnerships, including a particularly successful professional relationship between PXE International and the Laboratory of Matrix Pathobiology at the University of Hawaii. This partnership was critical in discovering the PXE gene and in beginning the elucidation of the pathobiology of this genetic disorder. Examination of some of the elements of this partnership may be useful for other lay advocacy/professional collaborations.

A consumer perspective on informed consent and third-party issues.

Our two children were diagnosed with a rare genetic disorder, which led us to establish a research foundation. This led to in-depth consideration of issues surrounding informed consent from a consumer perspective. Third-party issues arose as central to the formulation of ethical policy in the establishment of a blood and tissue bank and an epidemiologic study. We suggest that a number of myths--privacy is possible, samples can be stripped of identifiers, humans are subjects, voluntary informed consent is attainable, genetics is about the individual only, genetic information is different than other medical information, research is altruistic, the public will learn truths about genetic research via media, and research is culturally competent--make it difficult to resolve the issues intrinsic to informed consent. A number of important elements could make policy decisions less complicated. These include conducting culturally competent research; conveying noncoercive hope, not hype; contacting the voluntary informant only; asking the informant to extend contact to other family members; requiring a comprehensive informed consent process for all contacted; and engaging in state-of-the-art data protections. There is a need for a "Genomic Hippocratic Oath," creating an ethical basis for research similar to the one vowed by health care professionals. Establishing ethical policies as a result of the collaboration of policy makers, researchers, and consumers will allow research to progress ethically at a rapid rate. If regulations are oppressive, they will thwart research; if they are too lenient, participants will not receive protections needed to participate safely.

Empowering the public to be informed consumers of genetic technologies and services.

OBJECTIVE: The genetics community, together with lay advocacy organizations and the general public, should strategically plan a focused, culturally competent, community-based public genetic literacy program. METHODS: Inclusive of all stakeholders (consumers, professionals, disability communities, disenfranchised communities), society can advance this objective through a proactive, focused and coordinated outreach to build public awareness and understanding. RESULTS: Genetic Alliance programs support consumers with genetic disorders, raise health professional awareness of their concerns, educate the public about emerging genetic information and technologies, increase access to high quality information resources, and advocate for public policies that ensure the promises of genetics. CONCLUSION: The challenge before the genetics community is to be proactive, clear, and inclusive. The public should be empowered to make informed choices, allowing the potential benefits of genetic technologies and services to become manifest in improved healthcare and quality of life.