Eukaryotic cell organelles

http://www.jeffdonofrio.net/DNA/DNA_Analysis.html

Inheritance• Each cell has MANY mitochondria

• Oocytes have many mitochondria

• Sperm mitochondria are specialized, jettisoned at fertilization

• Mitochondria are only MATERNALLY inherited

Mitochondrial Function• Energy production- via Krebs Cycle ATP

• Glucose pyruvate = 2 ATP

• Pyruvate CO2 and H20 = 34-36 ATP

• Calcium homeostasis

• Role in apoptosis

• Role in blood and hormone synthesis

• Main tissues with high energy needs• Brain, heart, liver, muscles, respiratory,

endocrine

Human mitochondrial genome

Nageswara R. Madamanchi, and Marschall S. Runge Circulation Research. 2007;100:460-473

Copyright © American Heart Association, Inc. All rights reserved.

37 genes ~17,000 bp• 13 polypeptides, • 22 tRNAs,• 2 rRNAs).

Mitochondrial Dysfunction• Loss of motor control

• Muscle weakness

• Seizures

• Visual and auditory problems

• Poor growth

• Cardiac disease

• Liver disease

• Developmental delays

• Susceptibility to Infection

Variants in mitochondrial genes variety of diseases• 1 in 200-250 live births has a potentially

pathogenic mitochondrial DNA mutation Often

• delayed onset• Not directly lethal

• 45 listed on site- United Mitochondrial Disease Foundation diseases of mitochondrial function -www.umdf.org

Could Replacement of Mom’s Mitochondria Repair the Problem?

During Female embryonic

development

After pubertyAt each cycle

Overview of spindle-chromosomal complex transfer

Videomms://media.ohsu.edu/host/hosp/replacement.wmv

Healthy Baby

IVF required for embryo development

(Photo Credit: Mr. J. Conaghan)

http://stemcells.nih.gov/info

Placenta Embryo

Mitochondria appear everywhere except near the chromosomes

Visualization of the spindle during enucleation avoids damage

Spindle-chromosomal complex successfully isolated

Karyoplast contains ~1.5% volume compared to a cytoplast

Karyoplast inserted into perivitelline space

Karyoblast with patient’s spindle

Fusion using Sendai virus extract yields metaphase II chromosomes

Movie

mms://media.ohsu.edu/host/hosp/replacement.wmv

Chronology of innovation• Late 1990s: Cytoplasmic transfer leads to ~100 births

worldwide• 2001: FDA halts cytoplasmic transfer• September 2009: Mitochondrial gene replacement in

primate offspring and embryonic stem cells• May 2010: Pronuclear transfer in non-viable human

embryos• October 2012: Mitochondrial gene replacement in

human embryos to blastocyst stage• January 2013: Two additional studies demonstrating

feasibility in human

Success rate: 4 healthy births

Mito and Tracker

15 spindle-transfer embryos implanted into

9 recipients

Sequencing confirms mixed parentage

Pronuclear transfer is an alternate approach

Some mitochondria may also be transferred