NF1NF1NeurofibromatosisNeurofibromatosis

Presented by:Presented by:

Jacqueline HoltJacqueline Holt

March 4March 4thth 2003 2003

ObjectivesObjectives

Identity NF1 geneIdentity NF1 gene Biochemistry of NF1Biochemistry of NF1 Mutations in NF1Mutations in NF1 NF1 and cancer (Neurofibromatosis)NF1 and cancer (Neurofibromatosis)

Located on chromosome Located on chromosome 17q11.217q11.2

Identity NF1 geneIdentity NF1 gene

NF1 expressed in all tissues of NF1 expressed in all tissues of human, rat, mouse; higher in human, rat, mouse; higher in nervous tissuesnervous tissues

Encodes a protein Neurofibromin Encodes a protein Neurofibromin made of 2839 amino acids; 220kDmade of 2839 amino acids; 220kD

Biochemistry NF1Biochemistry NF1

Neurofibromin- most abundant in Neurofibromin- most abundant in nervous systemnervous system

Large and complex signaling proteinLarge and complex signaling protein

Tumor Suppressor in nervous systemTumor Suppressor in nervous system

Biochemistry of NF1Biochemistry of NF1

Contains a functional GAP-related domain Contains a functional GAP-related domain (GRD)(GRD)

Biochemistry of NF1Biochemistry of NF1

Homologous to the Homologous to the GTPase activating GTPase activating protein (GAP) protein (GAP) family member: family member: p120rasp120ras

GAP proteins turn GAP proteins turn off the ras signal off the ras signal by converting GTP by converting GTP (active) to GDP (active) to GDP (inactive)(inactive)

RAS PathwayRAS Pathway

Ras regulates Ras regulates proliferation and proliferation and differentiationdifferentiation

NF1 PathwayNF1 Pathway

NF1 appears to be NF1 appears to be a negative a negative regulator of the regulator of the RAS signal RAS signal transduction transduction pathway via its pathway via its GAP activity GAP activity domain domain

Tumor suppressorTumor suppressor

NF1 Knockout MiceNF1 Knockout Mice

NF1 heterozygous (NF1 NF1 heterozygous (NF1 +/-+/-) are viable, ) are viable, but develop malignancies; myeloid but develop malignancies; myeloid leukemia leukemia

Homozygous (NF1 Homozygous (NF1 -/--/-) died with heart ) died with heart defectsdefects

Helped with characterization of NF1 Helped with characterization of NF1 function in cell types that are function in cell types that are affected in NF1 tumorsaffected in NF1 tumors

Mutations in NF1Mutations in NF1

Mutation in one copy is enough to Mutation in one copy is enough to produce benign tumors and other produce benign tumors and other symptomssymptoms subcutaneoussubcutaneous

Need mutation in both copies of Need mutation in both copies of alleles to form malignant tumorsalleles to form malignant tumors MPNST (malignant peripheral nerve MPNST (malignant peripheral nerve

sheath tumor)sheath tumor)

Mutations in NF1Mutations in NF1

Examination of NF1 malignant tumor cell Examination of NF1 malignant tumor cell lines showed a decrease or absence of lines showed a decrease or absence of neurofibromin expressionneurofibromin expression

Loss of function results in deregulation of Loss of function results in deregulation of Ras activityRas activity

Results in high levels of active Ras-GTPResults in high levels of active Ras-GTP Results in increase in cell proliferationResults in increase in cell proliferation Schwann cells are primary target for Schwann cells are primary target for

mutationmutation

Test Test NeurofibrominNeurofibromin Activity in a Cell! Activity in a Cell!

NF1 and p16NF1 and p16

p16 is a CDKI; prevents cyclinD binding to p16 is a CDKI; prevents cyclinD binding to cdk4cdk4

Analyzed cells with malignant and benign Analyzed cells with malignant and benign peripheral nerve tumorsperipheral nerve tumors

Found that benign tumors did not have p16 Found that benign tumors did not have p16 deletionsdeletions

Malignant tumors had p16 deletionMalignant tumors had p16 deletion Malignant tumors associate with p16 Malignant tumors associate with p16

deletiondeletion

NF1 & NeurofibromatosisNF1 & Neurofibromatosis

Identified by Friedrich Recklinghausen 1882Identified by Friedrich Recklinghausen 1882 Most common inherited neurological diseaseMost common inherited neurological disease

Autosomal dominantAutosomal dominant 1 in 3,500- 4,0001 in 3,500- 4,000

50% cases are spontaneous50% cases are spontaneous 1 in 10,0001 in 10,000

Primarily affects the development and growth Primarily affects the development and growth of cells in nervous systemof cells in nervous system

NF1 & NeurofibromatosisNF1 & Neurofibromatosis

2 major manifestations:2 major manifestations:

Neurofibromas and gliomas- benign Neurofibromas and gliomas- benign tumors along peripheral and optic tumors along peripheral and optic nerves nerves

NeurofibromasNeurofibromas

Contain 4 cell typesContain 4 cell types Schwann cellsSchwann cells NeuronsNeurons FibroblastsFibroblasts PerineurialPerineurial

3 kinds of Tumors3 kinds of Tumors Cutaneous Cutaneous Interneural Interneural PlexiformPlexiform

Café-au-lait spotsCafé-au-lait spots

11stst symptoms of symptoms of NF1NF1 Important for Important for

diagnosisdiagnosis BenignBenign

Other symptoms include:Other symptoms include: Lisch nodulesLisch nodules Short statureShort stature SeizuresSeizures Learning and behavior dysfunctionLearning and behavior dysfunction Juvenile myeloid leukemiaJuvenile myeloid leukemia Defects in bone structureDefects in bone structure

Other symptoms include:Other symptoms include: Lisch nodulesLisch nodules Short statureShort stature SeizuresSeizures Learning and behavior dysfunctionLearning and behavior dysfunction Juvenile myeloid leukemiaJuvenile myeloid leukemia Defects in bone structureDefects in bone structure

Life expectancy 10-Life expectancy 10-15 years15 years

Malignancy most Malignancy most common cause of common cause of deathdeath

Treatments:Treatments: Laser removal of Laser removal of

neurofibromasneurofibromas Back braces or Back braces or

surgerysurgery Educational Educational

interventionintervention RadiationRadiation ChemotherapyChemotherapy