Stem cells are the body’s master cells, with the potential to develop into many different cell types.
2 general properties:
Make copies of themselves
Differentiate or develop into more specialized cells
2 major types:
Embryonic: pluripotent, meaning they can become any cell in the body
Adult: limited differentiation, meaning they can only develop into a specific type of cell
Induced pluripotent (iPSC): derived by reprogramming somatic cells
Key Foci:
Research objectives include developing methods for generating specific cell types from stem cells, understanding stem cell biology, exploring potential for organ regeneration, and investigating the use of stem cells in drug development and disease modeling.
Classification of Stem Cells:
Totipotent Cells: Can give rise to any cell type, including extra-embryonic tissues; e.g., a zygote.
Pluripotent Cells: Can become any cell type within the embryo; e.g., ESCs and iPSCs.
Multipotent Cells: Limited to differentiating into a set of related cell types; e.g., hematopoietic stem cells from bone marrow.
Understanding Cloning in STEM:
Cloning refers to creating a genetically identical copy of an organism or cell.
Uses techniques such as somatic cell nuclear transfer (SCNT) and gene cloning.
Significant Achievements:
Major developments include Dolly the sheep, the first mammal cloned from an adult somatic cell (1996).
Therapeutic Cloning
Aims to produce embryonic stem cells that are genetically identical to the patient, reducing rejection risk for transplants.
Methods studied include creating blastocysts from somatic cells and harvesting stem cells for therapy.
Reproductive Cloning
The transfer into the uterus with the intent to establish a pregnancy.
Offspring is genetically identical to the donor of the transferred nucleus.
Cloning For Research
Cloning animal models of disease
Create genetically engineered animals to produce drugs or proteins
Produce human antibodies, proteins to fight pathogens
Overview of Induced Pluripotent Stem Cells:
iPSCs are somatic cells that have been reprogrammed to a pluripotent state.
They can generate patient-specific stem cells without creating embryos
Key Factors in Pluripotent Conversion:
4 transcription factors, Oct4, Sox2, Klf4, and c-Myc, are able to reprogramming cells. Techniques like viral transduction and non-viral methods such as plasmid transfection improve safety and efficiency in generating iPSCs.
Considerations in Clinical Use:
Advantages: Ethical appeal, potential for patient-specific therapies, and a reduced risk of immune rejection.
Disadvantages: Mutagenesis risk, potential for tumor formation, and the need for strict control in differentiation to achieve desired cell types.
Research Strategies for Heart Disease:
Research efforts concentrate on cardiac stem cell therapy's role in regeneration, addressing challenges such as delivery methods, cell survival post-transplant, and differentiation into functional heart tissue to restore heart function post-infarction.
Potential Complications:
Tumorigenicity (the formation of tumors)
Migration from the site of transplantation
Increased immunological incompatibility
Death of transplanted cells
Purpose: to detect early disease or risk factors for disease in large numbers of apparently healthy individuals, not intended to provide definitive diagnosis
Population-based screening;
Pap smear, mammograms, prostate exam, colonoscopies
Genetic screening:
Newborn, carrier, and prenatal screenings
Validity of Screening Tests:
Sensitivity: ability of a test to correctly identify those who truly have the disease.
% of diseased individuals who have positive test results
Specificity: the ability of a test to correctly identify those who do not have the disease, thus reducing false positive results.
% of non-diseased individuals who have negative test results
Positive Predictive Value (PPV): likelihood that someone who tests positive is truly positive.
High PPV indicates a small % of false positives among those who test positive
Negative Predictive Value (NPV): likelihood that someone who tests negative is truly negative.
High NPV indicates a small % of false negatives among those who test negative
Genetic testing of asymptomatic couples for carrier status of common genetic diseases to determine reproductive risks
Began as ethic bases screening, now is universal
Challenges:
Access to testing: Ensuring equitable access for all populations, particularly underserved communities.
Interpretation of results: Variability in understanding and communicating genetic information to patients.
Psychological impacts: Addressing the emotional burden of potential risk and decision-making following results.
Evaluating embryos during IVF for genetic abnormalities prior to implantation to reduce the risk of inherited conditions.
Goal: decrease chance of miscarriage or chromosomal abnormalities
Goal: to identify individuals who are at increased risk to have a child with a genetic condition
Population:
May reduce diagnostic tests in high risk populations
May increase diagnostic tests in general populations
1st Trimester Screen:
10-14 weeks
Utilizes maternal serum markers and ultrasound to assess the risk of chromosomal abnormalities.
2nd Trimester Screen:
16-24 weeks
Diagnostic for many organ malformations
~15% false positive rate
Non-Invasive Prenatal Screen:
After 8 weeks
A blood test that analyzes fetal DNA in the mother's blood
Can assess the risk of chromosomal abnormalities
Offers a higher detection rate with lower false-positive rates compared to traditional screening methods.
Goal: diagnose genetic disorders early in life to ensure timely intervention and management.
Process:
Blood (from heel-prick) sent to a state-run laboratory
Physician notified of abnormal results
Physician informs parents and discusses follow-up plan
Purpose: To confirm, or determine the presence of disease in an individual suspected of having the disease
Symptomatic:
Used to confirm or rule out suspected genetic disease in a symptomatic individual
May provide information for medical management or risk to family members/future offspring
Asymptomatic/Predictive/Predisposition:
Used to determine a healthy person’s predisposition to develop disease
Testing usually sought based on family or medical history
Purpose: reveal order of bases present in the genome of an organism.
Types:
Single Gene Test:
one test looks for one condition
Multi-Gene Panel:
one test looks for many genes/conditions that have the same symptom
Exome:
Looks for mutations in a large percentage of known disease genes in exonic and flanking intronic regions (1-1.5% of the genome)
One test looks for thousands of disorders
25-30% diagnostic yield
Genome:
Looks for mutations in exon and intronic regions, including non-coding regions
40% diagnostic yield
Testing for epigenetic signatures:
Variant of uncertain significance (VUS) in a gene involved in transcriptional regulation/chromatin remodeling
RNA sequencing:
Has been done routinely on a clinical basis for hereditary cancer genes for a few years now
Can order from certain labs to help determine whether a VUS may be disease-causing
Deep sequencing for low level mosaicism:
Became clinically available within the last year
Used for conditions that are always mosaic or may be mosaic
Used for parents of a child with apparent de novo variant who want to know more accurate recurrence risk
80% of rare diseases are currently known to be genetic.
Conditions once thought to be environmental, but were proved to be genetic
Cerebral Palsy: once thought to be due to birth injury, even though some did not show signs of injury
Autoimmune Disorders: previously considered to be entirely immune system-related, research has revealed HLA haplotypes that increase susceptibility and severity.
Traditional Model:
Geneticist + Genetic Counselor
Newer Models:
GC-first or GC-only
FHx of genetic disorder
Common neurodevelopmental indications
Specific phenotype with gene or gene panel available
Consenting for exome or genome sequencing
Nurse Practitioners or Physician Assistants
When physical exam or management is needed
Clinical intake
physical exam, PMHx, FHx
Laboratory/Imaging results
X-ray, MRI, sweat test, etc
Expertise of other specialists
Genetic testing
Pathognomonic Findings (least common)
A finding specific to a particular diagnosis
Clinical Diagnostic Criteria (occasional)
A written set of symptoms associated with a particular condition
Published in the medical literature
Suggestive Features (sometimes)
Non-Specific Symptoms (most common)
Patient perception of test
Genetic discrimination questions
Coping with uncertainty
Parental guilt
The process of receiving a diagnosis can be time-consuming and frustrating for families
Not all individuals seen in Genetics clinic receive a diagnosis
Impact of genetic diagnosis
Vascular Malformations
Capillary
Venous
Arteriovenous
Lymphatic
Generalized Lymphatic Anomaly (GLA)
Kaposiform Lymphangiomatosis (KLA)
Combined
Capillary Venous Lymphatic Malformations (CVLM)
Vascular Tumors
Benign
Hemangioma
Locally Aggressive
Kaposiform hemangioendothelioma (KHE)
Malignant
Angiosarcoma
Usually present at birth or in early life
Can affect different parts of the vascular system:
Arteries, Veins, Capillaries, Lymphatics
Expansive growth
Often do not involute
Can become symptomatic at any time in life:
Growth spurts, puberty, infection, trauma
Gene mutations identified in many vascular malformations
Mutations are in key cell signaling pathways & many are oncogenes (cancer causing) in other tissues
Somatic:
Non-germline somatic cells
Cannot be inherited
Mutation in tumor only
Germline:
Present in egg or sperm
Can be inherited
Cause cancer family syndrome
All cells become affected in offspring
Capillary Malformations:
Isolated “port-wine” (strawberry) birthmarks
GNAQ activating mutation
Venous Malformations:
Mutations on TIE2 (TEK)
over 95% of spontaneous venous malformations
Mutations in PIK3CA
30-50% of TEK-negative VMs
CVLM, CLOVES, & KTS:
CLOVES: Combination of vascular, skin, lipomatous overgrowth, and musculoskeletal abnormalities
Lipomatous masses cause asymmetric hypertrophy of the trunk and other areas of the body
Caused by somatic mutations in PIK3CA gene
Mosaic gain-of-function mutations
Can be treated with Alpelisib or Rapamycin