Genetic diseases are obviously caused by our genes. The progress in the field of genetics is constantly giving us new clues regarding the correlations between certain genetic types and a risk to develop some diseases.
Mitochondrial DNA (mtDNA) only represents a tiny fraction of a person's DNA. However, it plays an important role in the energy production within cells, and are hence referred to as the "powerhouses" of the cell. About 2 billion mitochondria are made every second throughout a person’s life, each having an average life of around 100 days.
MtDNA is exclusively inherited through the mother, and remains unchanged for many generations. Mutations occur randomly after anything between 10 and 50 generations. This makes it possible to classify human beings into haplogroups sharing a same number of mutations. Each individual thus belongs to a definite mtDNA haplogroup. Haplogroups can be further divided into more precise subclades, sharing more mutations and therefore a more recent common ancestor than with the whole haplogroup.
MtDNA subclades are mostly determined by mutations in the coding region of the DNA (i.e. having medical functions). Consequently, it is possible that one or several mutations found in a particular haplogroup or subclade have a positive or negative effect on health. For instance, one's haplogroup can influence cancer risk either protectively or detrimentally (see examples below).
The Mitomap website has a list of mtDNA mutations in associated with diseases. They can be sorted by Coding & Control Region mutations and rRNA/tRNA mutations.
These mutations are not revealed by the common HVR1 and HVR2 tests for genealogical purposes, but require to test the full mtDNA sequence.
Mitochondrial diseases are most often associated with energy-related conditions, such as myopathy (neuromuscular disease, leading to muscle paralysis) and cardiomyopathy (heart muscle disease), single nerve paralysis (notably the optical nerve), exercise intolerance, but also more benign symptoms like fatigue, overall weakness, headaches, or loss of appetite.
Other medical conditions related to mtDNA include osteoporosis, Alzheimer's disease, Parkinsons's disease, etc.
Examples of diseases associated with a haplogroup
Among European populations
The risks of developing Parkinson Disease have been found to be higher among mtDNA haplogroups H, but lower for haplogroups J and K.
Men belonging to haplogroup H have the lowest risk of asthenozoospermia (reduced sperm motility), while those of hpg T have the highest.
There is a correlation between haplogroup H and protection from sepsis.
Haplogroups I, J1c, J2, K1a, U4, U5a1 and T have lower incidences of Parkison's Disease. I, J and T also have increased longevity. However, haplogroups J and T have been associated with increased risk for expression of a maternally inherited blindness disorder (Leber hereditary optic neuropathy). This is especially true for the J2 subclade.
Haplogroup T is associated with coronary heart disease, but also a decreased risk of diabetes (source 1, source 2, source 3).
Haplogroup N is considered a risk factor for breast cancer. This also applies to all its sub-haplogroups (H, T, U, V, W, X) except for hpg K.
Mitochondrial haplogroup U is associated with an approximately 2-fold increased risk of prostate cancer and renal cancer.
Coskun et al. says that haplogroups J and UK are protective against Alzheimer's disease (AD), whereas haplogroup H is thought to increase the penetrance of AD. One of the mutations found in AD patient but not in controls was T414G.
Haplogroup U and its subclade K are associated with higher risks of strokes and Chronic Progressive External Ophthalmoplegia.
Haplogroup X has a defining mutation related to type-2 diabetes, cardiomyopathy and endometrial cancer risk.
Studies have suggested haplogroup IWX to be highly protective against AIDS progression.
The A10398G! (back mutation from macrohaplogroup N) has been associated with longevity, protection against PD, altered cell pH, metabolic syndrome, and increased risk of breast cancer. It is found in haplogroups J (except J1c8), K1, K2a11, N1a1 (including hg I), N8, W1e1a and W3a1d.
Among East Asian populations
Longevity is associated with haplogroup D. The mutations involved are C5178a (defining haplogroup D) and C8414T (defining D4/D1).
Haplogroups D4a and D5a are associated with higher risk of esophageal cancer.
Haplogroups F and A are genetic risk factors for diabetes, whereas haplogroup N9a was found to be a protective factor against Metabolic syndrome (cause of cardiovascular disease and diabetes), especially for women.
Haplogroup M7b2 was found to be a genetic risk factor for leukemia.
People belonging to haplogroups B4c, G1 and H4 are more predisposed to obesity.
Members of haplogroup G (found in North-East Siberia) have increased risks of Non-Insulin Dependent Diabetes Mellitus.
Such studies are still in their infancy. The years, and indeed decades to come will shed more light on the relation between diseases and genes. What is more, the results of these studies are not easily accessible to the general public, or are often too technical to be easily understood for lay people. But if you find some interesting data, feel free to post it here as a summary of the information jungle in which we live.
Mitochondrial DNA (mtDNA) only represents a tiny fraction of a person's DNA. However, it plays an important role in the energy production within cells, and are hence referred to as the "powerhouses" of the cell. About 2 billion mitochondria are made every second throughout a person’s life, each having an average life of around 100 days.
MtDNA is exclusively inherited through the mother, and remains unchanged for many generations. Mutations occur randomly after anything between 10 and 50 generations. This makes it possible to classify human beings into haplogroups sharing a same number of mutations. Each individual thus belongs to a definite mtDNA haplogroup. Haplogroups can be further divided into more precise subclades, sharing more mutations and therefore a more recent common ancestor than with the whole haplogroup.
MtDNA subclades are mostly determined by mutations in the coding region of the DNA (i.e. having medical functions). Consequently, it is possible that one or several mutations found in a particular haplogroup or subclade have a positive or negative effect on health. For instance, one's haplogroup can influence cancer risk either protectively or detrimentally (see examples below).
The Mitomap website has a list of mtDNA mutations in associated with diseases. They can be sorted by Coding & Control Region mutations and rRNA/tRNA mutations.
These mutations are not revealed by the common HVR1 and HVR2 tests for genealogical purposes, but require to test the full mtDNA sequence.
Mitochondrial diseases are most often associated with energy-related conditions, such as myopathy (neuromuscular disease, leading to muscle paralysis) and cardiomyopathy (heart muscle disease), single nerve paralysis (notably the optical nerve), exercise intolerance, but also more benign symptoms like fatigue, overall weakness, headaches, or loss of appetite.
Other medical conditions related to mtDNA include osteoporosis, Alzheimer's disease, Parkinsons's disease, etc.
Examples of diseases associated with a haplogroup
Among European populations
The risks of developing Parkinson Disease have been found to be higher among mtDNA haplogroups H, but lower for haplogroups J and K.
Men belonging to haplogroup H have the lowest risk of asthenozoospermia (reduced sperm motility), while those of hpg T have the highest.
There is a correlation between haplogroup H and protection from sepsis.
Haplogroups I, J1c, J2, K1a, U4, U5a1 and T have lower incidences of Parkison's Disease. I, J and T also have increased longevity. However, haplogroups J and T have been associated with increased risk for expression of a maternally inherited blindness disorder (Leber hereditary optic neuropathy). This is especially true for the J2 subclade.
Haplogroup T is associated with coronary heart disease, but also a decreased risk of diabetes (source 1, source 2, source 3).
Haplogroup N is considered a risk factor for breast cancer. This also applies to all its sub-haplogroups (H, T, U, V, W, X) except for hpg K.
Mitochondrial haplogroup U is associated with an approximately 2-fold increased risk of prostate cancer and renal cancer.
Coskun et al. says that haplogroups J and UK are protective against Alzheimer's disease (AD), whereas haplogroup H is thought to increase the penetrance of AD. One of the mutations found in AD patient but not in controls was T414G.
Haplogroup U and its subclade K are associated with higher risks of strokes and Chronic Progressive External Ophthalmoplegia.
Haplogroup X has a defining mutation related to type-2 diabetes, cardiomyopathy and endometrial cancer risk.
Studies have suggested haplogroup IWX to be highly protective against AIDS progression.
The A10398G! (back mutation from macrohaplogroup N) has been associated with longevity, protection against PD, altered cell pH, metabolic syndrome, and increased risk of breast cancer. It is found in haplogroups J (except J1c8), K1, K2a11, N1a1 (including hg I), N8, W1e1a and W3a1d.
Among East Asian populations
Longevity is associated with haplogroup D. The mutations involved are C5178a (defining haplogroup D) and C8414T (defining D4/D1).
Haplogroups D4a and D5a are associated with higher risk of esophageal cancer.
Haplogroups F and A are genetic risk factors for diabetes, whereas haplogroup N9a was found to be a protective factor against Metabolic syndrome (cause of cardiovascular disease and diabetes), especially for women.
Haplogroup M7b2 was found to be a genetic risk factor for leukemia.
People belonging to haplogroups B4c, G1 and H4 are more predisposed to obesity.
Members of haplogroup G (found in North-East Siberia) have increased risks of Non-Insulin Dependent Diabetes Mellitus.
Such studies are still in their infancy. The years, and indeed decades to come will shed more light on the relation between diseases and genes. What is more, the results of these studies are not easily accessible to the general public, or are often too technical to be easily understood for lay people. But if you find some interesting data, feel free to post it here as a summary of the information jungle in which we live.
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