FANCD2 FANCONI ANEMIA PROTEIN COMPLEMENTATION GROUP D2 by Meredith Binkley

Fanconi Anemia as a disease  Rare new cases in the US each year  Symptoms include hematological abnormalities (anemia), radial and thumb hyperplasia, café au lait spots, short stature, infertility  Other less severe symptoms include unexplained fatigue, nose bleeds, and easy bruising

Leukemia and squamous cell carcinoma are commonly associated with Fanconi Anemia People with Fanconi Anemia fail to develop leukocytes, red blood cells and platelets Fanconi Anemia creates a predisposition to cancer

Bone marrow transplantation is a treatment but this increases the chance of cancer Inherited in an autosomal recessive disorder

 FA cells have a hypersensitivity to DNA damaging chemicals. This results in apoptosis.  FANCD2 is part of a family of FANC proteins  A mutation in different FANC proteins can result in Fanconi Anemia The cellular phenotype

History of FANCD2 and FA  Discovered by Guido Fanconi in 1927  In 1992 Strathdee et al. conducted a study suggesting that there was more than one gene that caused the disease. He discovered 4 complementation groups  2001 Timmers et al was the first to clone FANCD2 via positional cloning. They also discovered the heterogeneous nature of FANCD.  2001, Alan D'Andrea linked FANCD2 to BRCA1 “Fluorescence microscopy shows that D, usually diffusely located throughout the nucleus (top left), concentrates into nuclear foci after DNA damage (top right).” Focus, Harvard’s Medical Journal

The two pathways with FANCD2 In response to Ionizing radiation, FANCD2 is phosphorylate d In response to Mitomycin C a monoubiquitin ation event occurs

A closer look at both pathways ATM pathway occurs due to a double stranded break BRCA1 pathway occurs when homologous recombination can fix the situation.

The FANCD2/ BRCA pathway  A nuclear core complex monoubiquitinates FANCD2  Monoubiquitinatio n in response to DNA damage activates the protein  FANCD2 then takes actions to help with HR

A closer look at the NCC  FANCA, FANCB, FANCC, FANCE, FANCF, FANCG, FANCL AND FANCM all group together  FANCL is the actual protein that monoubiquitinates FANCD2

The FANCD2/ ATM Pathway  Activated in response to a double stranded break  Believed to be connected to S- phase check point, but exact link is unknown  FA cells spend times longer ins late s-phase arrest after cross linking

“Perhaps FANCD2, with signaling input from the FA proteins and ATM, may determine the choice between these alternative pathways.” - Markus Grompe, Department of Molecular and Medical Genetics Oregon Health Science University Portland

Now that we know the function, how does it cause cancer?  Tumor formation is not completely understood with FANC family of proteins  It takes more than one mutation to lead to cancer  FANC mutations elevate apoptosis  It is hypothesized that a mutation of a resistance to apoptosis will be selected for at a cellular level  A mutation in p53 that causes cells to avoid apoptosis will be selected for  There are high alterations of p53 in sporadic tumors in FA patients  More evidence in mouse mutants that also had a heterozygous p53 gene

Double mouse mutants  Took FANCD2 knock out mice  Crossed them with p53 null mutant mice  Came up with a FANCD2-/-/p53 +/- double mutant mouse  These mice developed tumors much earlier than FANCD2-/- mice Scott Houghtaline and colleges at the Oregon Health and Science University

More on Mice Mutants  In 2000, Cheng et al created FANCA knockout mice  Viable with no development abnormalities  Had a slightly decreased platelet count, hypogonadism and impaired fertility  Also had chromosomal instability and were sensitive to Mitomycin C  However, FANCD2 mouse mutants are smaller, develop epithelial tumors and are germ-cell deficient  Oddly, there are no defects in the ATM mediated s-phase checkpoint

Treatments  A treatment for the FA disease is a bone marrow transplant  However finding a match can be hard.  Hormones can stimulate blood cell production  Enbrel drug therapy- block tumor necrosis factor (TNF)  Used in arthritis and people with immune disease  Has lots of negative side effects for FA patients: lower ability to fight infections, increases change of leukemia Cincinnati Children’s Hospital

Henry was a boy who suffered from Fanconi Anemia. His parents wanted him to have a bone marrow transplant but could not find a donor. They decided to have another baby. Naturally the baby would have an 18% chance of matching Henry and not having Fanconi anemia. Mark Hughes, from the National Institute of Health was going to test the embryo at the eight cell stage before it was implanted. This would give the couple a second child without FA and would save their first child’s life. Hughes’ work was stopped after it was revealed in 1997 that he was violating a federal ban on human embryo research. Henry never received his sibling and died on December 11, His parents later formed A Hope for Henry an organization that donated toys to children in hospitals. Henry’s story…putting a face to the disease “Vetoing Henry,” The Washington Post

 Eike Gallmeier and Scott E. Kern, “Targeting Fanconi Anemia/BRCA2 Pathway Defects in Cancer: The Significance of Preclinical Pharmacogenomic Models,” Clinical Cancer Research 13, 4-10, January 1, 2007  Alan D.D’Andrea* and Markus Grompe‡, “THE FANCONI ANAEMIA/BRCA  PATHWAY,” Nature. VOLUME 3, JANUARY  Markus Grompe, “FANCD2: A branch-point in DNA damage response?” Medicine 8, (2002).  Scott Houghtaling, “Epithelial cancer in Fanconi anemia complementation group D2 knockout mice,” Genes & Dev. published online Jul 31,  Gurtan, A. D’Andrea, A. “Dedicated to the core: Understanding the Fanconi anemia complex” Elsevier pg  Thompson, L. Hinz, J. Yamada, N. Jones, N. “How Fanconi anemia proteins promor the four Rs: Replication, Recombination, Repair and Recovery.” Environmental and Molecular Mutagenesis pgs  Houghtaling, S. et al. “Heterozygosity for p53 Accelerates epithelial Tumor Formation in Fanconi Anemia complementation group D2 knockout Mice.” Molecular Biology, Pathobiology and Genetics. January 1, Work Cited