### MTHFD1 Gene Overview
The MTHFD1 gene (Methylenetetrahydrofolate Dehydrogenase 1) encodes a trifunctional enzyme that plays a critical role in one-carbon metabolism. It is crucial for the interconversion of various forms of tetrahydrofolate (THF), which are essential for the synthesis of nucleotides and amino acids, particularly in the context of methionine, thymidylate, and purine synthesis.

### 1. Associated Genes
MTHFD1 is associated with various genes involved in folate metabolism and related pathways. Key associated genes that may interact functionally or are part of similar metabolic pathways include:

- **MTHFR (Methylenetetrahydrofolate Reductase):** This gene is involved in the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate.
- **FOLR1 (Folate Receptor 1):** Involved in the uptake of folate into cells.
- **SHMT (Serine Hydroxymethyltransferase):** This gene links serine metabolism to folate metabolism.
- **GART (Phosphoribosylglycinamide formyltransferase):** Part of the de novo purine biosynthesis pathway.

### 2. Aging and Age-Related Diseases
MTHFD1 has been implicated in several age-related conditions due to its role in one-carbon metabolism and DNA synthesis. Some key associations include:

- **Neurodegenerative Disorders:** Variants in the MTHFD1 gene have been studied in relation to Alzheimer's disease and other forms of dementia. Impaired folate metabolism may affect homocysteine levels, and elevated homocysteine is a risk factor for cognitive decline.
- **Cancer:** Alterations in folate metabolism can influence cancer development and progression. Abnormal MTHFD1 activity may contribute to the deregulation of nucleotide synthesis, promoting tumorigenesis.
- **Cardiovascular Disease:** Elevated homocysteine levels due to impaired one-carbon metabolism can be linked to cardiovascular risks and conditions associated with aging.

### 3. Drug Interactions
Several drugs and classes of drugs may interact with pathways involving MTHFD1:

- **Antifolate Drugs:** Methotrexate and other antifolate agents can inhibit dihydrofolate reductase and may indirectly impact MTHFD1 activity through their effects on folate levels.
- **Vitamin Supplements:** Folic acid supplementation can modulate the activity of enzymes involved in the folate cycle, including MTHFD1, thus potentially enhancing its function.

### 4. Pathways and Biological Processes
MTHFD1 is involved in several important pathways within cellular metabolism:

- **One-Carbon Metabolism:** MTHFD1 is a key enzyme in this pathway, facilitating the conversion of THF derivatives, which are crucial for nucleotide and amino acid synthesis.
- **Purine Metabolism:** The activity of MTHFD1 directly impacts purine biosynthesis through the generation of 10-formyltetrahydrofolate.
- **Thymidylate and Methionine Biosynthesis:** The enzyme supports the generation of precursors necessary for DNA synthesis and methylation cycles, which are vital for cell division and function.
- **Amino Acid Metabolism:** MTHFD1 contributes to serine and methionine biosynthesis, linking folate metabolism to amino acid availability.

In summary, the MTHFD1 gene is critical for one-carbon metabolism, with functional implications in various metabolic processes and associations with age-related health conditions, drug interactions, and complexes with other genetic pathways.