Human glial fibrillary acidic protein (GFAP) promoter

2.2 kb fragment (-2163 to +47) of the human GFAP gene 5'-flanking region that restricts transgene expression to astrocytes in the CNS. Established for astrocyte-specific gene delivery in transgenic mice and AAV vectors; native GFAP promoter activity increases following brain or spinal cord injury as part of reactive astrogliosis, and a compact 681 bp derivative (gfaABC1D) is preferred when AAV packaging capacity is limited.

Length: 2178 bp

Strength: moderate

Tissue: Astrocytes in CNS; off-target expression reported in a subset of cortical neurons with AAV5 delivery, varying by brain region

Expression: constitutive

Origin: Human GFAP gene, -2163 to +47 5'-flanking fragment

Characteristics

In transgenic mice, this 2.2 kb human GFAP 5'-flanking fragment (gfa2) linked to a lacZ reporter drives astrocyte-restricted expression throughout the CNS, and transgene activity increases following brain injury, mirroring induction of endogenous GFAP during reactive astrogliosis. A truncated 681 bp derivative, gfaABC1D, reproduces essentially the same expression pattern with about twofold greater activity, making it preferred for AAV vectors where packaging capacity is limited. In AAV5 vectors, GFAP-promoter constructs also drive detectable off-target expression in a subset of cortical neurons (e.g., motor and medial prefrontal cortex), with the degree of neuronal leakage varying by brain region.

Applications: Used to restrict reporter and effector transgene expression to astrocytes in transgenic mouse brain and in AAV vectors delivered to rodent CNS, and as a reactive-gliosis reporter that is transcriptionally activated following brain and spinal cord injury.

Limitations: Not fully astrocyte-restricted in AAV vectors — AAV5-packaged GFAP-promoter constructs produce off-target expression in a subset of cortical neurons, with the degree of leakage differing by brain region. Endogenous GFAP promoter activity increases after CNS injury, so reactive astrogliosis can raise transgene expression above baseline in disease or injury models, confounding dose-controlled experiments. The full 2.2 kb fragment is larger than the compact gfaABC1D derivative, a consideration when AAV packaging capacity is limited.

Sequence

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References

  1. Brenner et al. (1994). GFAP promoter directs astrocyte-specific expression in transgenic mice. J Neurosci - Brenner 1994 GFAP Astrocyte
  2. Enbar et al. (2024). Regionally distinct GFAP promoter expression plays a role in off-target neuron expression following AAV5 transduction. Sci Rep - Enbar 2024 GFAP Off-Target Neurons