SIRPB1-SIRPD readthrough protein

The SIRPB1-SIRPD readthrough is a **novel fusion transcript** discovered via long-read RNA sequencing in human disease tissue, notably in granuloma-associated macrophages of individuals with cutaneous sarcoidosis and sarcoid myopathy[1]. This transcript arises from a "readthrough" event between the neighboring SIRPB1 and SIRPD genes, and produces a putative fusion protein that combines amino-terminal regions of **Signal-regulatory protein beta-1** (SIRPB1) with the carboxy-terminal region of **Signal-regulatory protein delta** (SIRPD)[1]. Unlike canonical SIRPB1, the predicted SIRPB1-SIRPD protein lacks the transmembrane and cytoplasmic domains required for its function as a cell-surface receptor, suggesting it likely acts as a soluble secreted protein, not as a classical cell-surface receptor[1]. Importantly, this fusion transcript is not a canonical, well-characterized protein nor an established therapeutic target, but recent research found it highly overexpressed in disease-related macrophages, with preliminary evidence supporting its use as a *diagnostic biomarker* for sarcoid myopathy (AUC ~0.985 in initial cohorts)[1]. There is **no current evidence for drug targeting**, disease-modifying function, or mechanistic understanding; its discovery is recent and its role in pathophysiology and as a therapeutic target remains uncharacterized. Standard molecular classifications do not apply, and its presence in reference databases is as a "readthrough" or "fusion transcript", not a canonical gene or receptor. **Note:** This entry does not correspond to a well-established protein, receptor, enzyme, or validated drug target. Its clinical and mechanistic relevance requires further study. The gene designation ENSG00000260861 reflects this readthrough event and not a conventional therapeutic target[1]. **Clarification and limitations:** - This entity is not a classical receptor, enzyme, transporter, or known target, nor is it a canonical, validated therapeutic target in pharmacology or drug discovery. - Use of this entry in structured drug-target datasets is discouraged; more study is needed to define its molecular and clinical relevance[1]. - If referencing the conventional SIRPB1 or SIRPD proteins, separate structured entries must be made for those human proteins, as they have established molecular identity and functional roles[2][3][4].

Other names

SIRPB1–SIRPD read-through transcriptENSG00000260861