Table 1.

Matrix metalloproteinase-9 expression in CNS development.

Brain region	Developmental window	Peak of MMP-9 expression	MMP-9 in experience dependent plasticity	Reference
Retinotectal Axons Visual Cortex Optic Nerve	Retinotectal map formation: P0–P21 (first 3 postnatal weeks) r. Monocular deprivation: P21–P28 r.; Postnatal week 3–5 r.; P19–P32 m. Optic nerve myelination: P7–P9 m.	Sup. Colliculus: P0–P10 protein P0–P14 activity. Optic Nerve: P7-P11 activity. P7 mRNA	Monocular enucleation increases MMP-9 enzymatic activity in SC Monocular deprivation increases MMP-9 mRNA in cortex	Oliveira-Silva et al. (2007) Fagiolini et al. (1994), Gordon and Stryker (1996), Spolidoro et al. (2012) Oh et al. (1999), Larsen et al. (2006)
Barrel Cortex	Thalamocortical input to Layer 4: P1-P4/5 m., r. Intracortical connections: Layer 4-2/3: P10-P14 r. Layer 2/3: thru adulthood r.		Whisker trimming in adolescent mice increases MMP-9 enzymatic activity; MMP-9 KO mice show reduced potentiation in L4 and L2/3 following trimming	Woolsey and Wann (1976), Kossut et al. (1988), Fox (1992), Maravall (2004), Kaliszewska et al. (2012)
Cerebellum	Granule cell proliferation, Climbing fibers refinement: Postnatal week 1 Granule cell migration; Parallel fiber innervation of Purkinje cells: Postnatal week 2–3 Purkinje cell arborization: Postnatal week 4	Granule precursors, Bergmann glia, Purkinje cells: P10 protein EGL, IGL and Purkinje cell layer: P11-P17 protein	MMP-9 KO mice at P12 exhibit: Decreased apoptosis of granule precursor cells; Delay in granule cell migration	r. Altman (1972a,b), r. Vaillant et al. (1999), r. Piccolini et al. (2012), m. Vaillant et al. (2003)
Hippocampus	Spontaneous activity and apoptosis: P0–P7 r. m. Mossy fiber development: first postnatal month r. Synapse elaboration: first postnatal month r.	Axon tips: P4 r. protein DG, CA1, CA3: P4 r. mRNA Postsynaptic densities: P8 r. protein	MMP-9 mediates cell survival through interactions with laminin MMP-9 KO mice show accelerated synaptic maturation MMP-9 treatment exaggerates immature spine morphology	Ribak et al. (1985), Steward and Falk (1991), Bilousova et al. (2009), Murase and McKay (2012), Aujla and Huntley (2014), Sidhu et al. (2014)
Auditory Cortex	Tonotopic reorganization: P11–P15 m. P11–P13 r. P9–P20 m. P11–P28 r.		Cochleotomy leads to increased MMP-9 levels in cochlear nucleus 1 day post-op	Zhang et al. (2002), de Villers-Sidani et al. (2007), Illing et al. (2010), Barkat et al. (2011), Kim et al. (2013)

r., rats; m., mouse; activity, enzymatic activity measure by zymography.