BLM CRISPR/Cas9 KO Plasmid (h): sc-400896

Overview

BLM (Bloom syndrome protein) is a RecQ family DNA helicase that preserves genome stability by resolving aberrant DNA structures arising during replication stress and recombination. It functions in DNA end resection and homologous recombination, suppresses crossover formation, and cooperates with the BTR complex (BLM–TOP3A–RMI1/2) to dissolve double Holliday junctions. BLM also interfaces with the Fanconi anemia network and ATR-dependent DNA damage signaling to coordinate replication fork restart and repair of stalled or collapsed forks. Loss of BLM activity is linked to elevated sister chromatid exchanges, chromosomal instability, and cancer predisposition phenotypes, making it a useful target for studying replication-associated DNA repair pathways.

BLM CRISPR/Cas9 KO Plasmid (h) is a pool of plasmids designed for targeted disruption of the BLM gene in human cell lines. Each plasmid in the pool co-expresses a unique sgRNA, targeting a distinct site within the BLM locus, alongside the Streptococcus pyogenes Cas9 nuclease, and encodes GFP to enable fluorescent identification and enrichment of successfully transfected cells. This multi-guide strategy increases the likelihood of inducing frameshifts or deletions that produce a functional knockout, offering a more robust alternative to single-guide approaches. DSBs induced at multiple sites are resolved through non-homologous end joining (NHEJ) or, when used with the included HDR donor template, homology-directed repair (HDR) at a defined target site within the locus.

When used in conjunction with the RFP-expressing HDR donor, GFP and RFP fluorescence can be used together to distinguish transfected from edited cell populations, streamlining flow cytometry-based sorting and clone selection workflows.

Homology-Directed Repair (HDR) Donor — Puromycin Cassette with RFP Reporter

For applications requiring confirmed, selectable knockout clones, BLM HDR Plasmid (h) includes an HDR donor construct containing a puromycin resistance cassette (PuroR) and a red fluorescent protein (RFP) reporter, flanked by homology arms specific to a defined BLM target site.
When co-transfected with BLM CRISPR/Cas9 KO Plasmid (h):

• The PuroR-RFP cassette integrates at the Cas9 cut site via HDR, disrupting the BLM open reading frame.
• RFP fluorescence provides an immediate visual indicator of successful integration, enabling fluorescence-based identification or sorting of edited cells prior to or alongside puromycin selection.
• Successfully edited cells are confirmed through puromycin resistance, substantially reducing clone screening burden.
• This selection strategy is ideal for generating stable, clonal KO cell lines for downstream functional studies, drug screening, or model development.

Cre-lox Cassette Removal System

The HDR donor construct features loxP sites flanking the PuroR-RFP selection cassette to allow clean marker removal following clone confirmation. Transient expression of Cre recombinase via the included Cre Vector: sc-418923 excises the cassette, leaving a minimal residual loxP site within the BLM locus and eliminating potential confounding effects on downstream assays.
This two-step approach:

• Minimizes disruption to local chromatin architecture and neighboring regulatory elements
• Restores a near-native genomic context at the edited locus
• Enables reuse of the puromycin selection strategy in the same cell line for additional edits

Key Features

• gRNA targeting BLM exon(s) critical for BLM function
• Co-expression of SpCas9 and sgRNA from a single plasmid for simplified delivery
• HDR donor with puromycin resistance for positive clone selection
• loxP-flanked PuroR cassette with Cre recombinase vector for seamless marker removal
• Supplied ready to use for delivery by transfection

For Research Use Only. Not Intended for Diagnostic or Therapeutic Use.