The KHDC4 gene encodes a protein that plays a significant role in RNA processing, specifically in pre-mRNA splicing. Here is a detailed overview based on your requests:

### 1. Associated Genes
KHDC4 may be linked to several genes involved in RNA processing and splicing. Some of these may include:
- **PRP19**: As mentioned in the summary, this gene is part of the spliceosomal complex and interacts with KHDC4.
- **SF3B1**: A component of the spliceosome that is also involved in mRNA splicing.
- **SNRNP proteins**: Associated with splicing factors and the spliceosome machinery.

Though specific associations can vary, the interplay between KHDC4 and these genes is crucial in the broader context of mRNA splicing.

### 2. Aging and Age-Related Diseases
While direct studies specifically linking KHDC4 to aging or age-related diseases may not be extensive, abnormalities in mRNA splicing often contribute to various age-related conditions, including:
- **Neurodegenerative diseases**: Mis-splicing may lead to protein aggregation, a common hallmark of conditions such as Alzheimer's disease.
- **Cancer**: Aberrant splicing is often observed in cancerous cells, potentially implicating KHDC4 in tumorigenesis as splicing factors like KHDC4 are involved in the regulation of splice site selection.

Further research may be necessary to pinpoint any direct causal relationships between KHDC4 and age-related pathology.

### 3. Known Drug Interactions
Currently, there may not be specific drugs or drug classes directly attributed to the modulation of KHDC4 function. However, given its role in pre-mRNA splicing:
- **Spliceosome inhibitors**: Compounds targeting the spliceosome may indirectly affect KHDC4's role in splicing, though specific inhibitors may not be well-characterized.
- **Chemotherapeutic agents**: Such agents that target abnormal splicing mechanisms in cancers might indirectly interact with spliceosome-associated proteins, including KHDC4.

### 4. Pathways and Biological Processes
KHDC4 is involved in various biological processes including:
- **mRNA Splicing**: The primary biological process, facilitating the removal of introns and joining of exons in pre-mRNA.
- **Regulation of Gene Expression**: By influencing which splice sites are selected, it plays a role in the gene expression landscape.
- **RNA Binding**: Engaging with A/C rich sequences in RNA suggests involvement in post-transcriptional regulation and stability of mRNA.

In terms of specific pathways, KHDC4's involvement in the spliceosome complex aligns it with:
- **Spliceosomal Assembly**: As a key component of the machinery that processes pre-mRNA.
- **Nuclear RNA Processing Pathways**: Involved in the processing of nuclear pre-mRNA before it is translated into proteins.

Overall, KHDC4 is an integral player in RNA splicing and may influence various biological processes, with broader implications in health and disease that warrant further exploration. Research can continue to uncover its potential roles in aging and associated conditions.