Table 1. Summary of abnormal dendritic spine phenotypes reported in Fmr1 KO mice.

The spine phenotypes reported in different brain regions of Fmr1 KO mice have been grouped according to three main results: increased density, normal density, and relative immaturity. Studies that used imaging in living neurons (in vivo or in acute/organotypic brain slices) are highlighted in gray.

Region →	Cortex	Hippocampus	Cerebellum	Olfactory bulb	Amygdala
Phenotype ↓
Increased spine density	Layer 2/3:	Pyramidal cells in CA1:		Granule cells:	Pyramidal-like neurons:
	Dolen et al., 2007 (P30)	Levenga et al., 2011a (25 weeks, CA1)		Scotto-Lomassese et al., 2011 (2 months)	Qin et al., 2011 (~3 months)
	Hayashi et al., 2007 (2 months)
	Liu et al., 2010 (12 weeks)
		Granule cells in dentate gyrus:
	Layer 5:	Grossman et al., 2010 (P15-60)
	Nimchinsky et al., 2001 (P7)
	℘Su et al., 2011 (1, 7, 8 weeks)	Whole hippocampus dissociated:
	Comery et al., 1997 (16 weeks)	Antar et al., 2006 (P0+16div)
	McKinney et al., 2005 (P60-90)	Swanger et al., 2011(E17+18div)
	Galvez & Greenough, 2005 (P73)
Normal spine density	Layer 2/3:	Pyramidal cells in CA1:	Purkinje neurons:
	Cruz-Martin et al., 2010 (P7–P21)	Grossman et al., 2006 (P60–P90)	Koekkoek et al., 2005 (adult)
	Meredith et al., 2007 (P14-23)
		Whole hippocampus dissociated:
	Layer 4:	Braun & Segal, 2000 (P0+7div)
	Harlow et al., 2010 (P7, P14)	Su et al., 2011 (P0+8 div)
		†Levenga et al., 2011b
	Layer 5:	(E16+14div)
	Nimchinsky et al., 2001 (P14, P28)	*Segal et al. 2003 (P1+14div)
		de Vrij et al., 2008 (E18+21div)
	Galvez & Greenough, 2005 (P25)
	Restivo et al., 2005 (12 weeks)
	Pan et al., 2010 (P30)
	Irwin et al., 2002 (60–90 days)
Relative immaturity of spines	Layer 2/3:	Pyramidal cells in CA1:	Purkinje neurons:	Granule cells:	Pyramidal-like neurons:
	Cruz-Martin et al., 2010 (P10-12; higher turnover; more filopodia / fewer mushroom spines)	Bilousova et al., 2009 (P7; more filopodia / fewer mushroom)	Koekkoek et al., 2005 (adult; longer)	Scotto-Lomassese et al., 2011 (2 months; longer)	Qin et al., 2011 (~3 months; longer)
		Grossman et al., 2006 (P60–P90; longer, more immature morphology)
	Meredith et al., 2007 (P14-23; longer)	¥Levenga et al., 2011a (25 weeks; more filopodia / fewer mushroom)
	Liu et al., 2010 (13 weeks; longer)
	Layer 5:	Granule cells in dentate gyrus:
	Su et al., 2011 (1, 2, 7, 8 weeks; longer)	Grossman et al., 2010 (P15–P60; more immature morphology)
	Nimchinsky et al., 2001 (P7–P28)	Whole hippocampus dissociated:
	Pan et al., 2010 (P20, P30; high turnover)
	Comery et al., 1997 (16 weeks; longer)	Antar et al., 2006 (P0+16div; longer, more filopodia / fewer spine synapses)
	Restivo 2005 (12 weeks; more immature morphology)	de Vrij et al., 2008 (E18+21div; longer, more filopodia / fewer mature spines)
	Irwin et al., 2002 (60–90 days; more immature morphology)	Su et al., 2011 (P0+8div; longer)
	Galvez & Greenough, 2005 (P73; longer, more immature morphology)	‡Levenga et al., 2011b (E16+14div; longer)
		Bilousova et al., 2009 (E15+14div; longer)
	McKinney et al., 2005 (P60–P90; longer, more immature morphology)	Swanger et al., 2011 (E17+18div; longer, more filopodia / fewer mushroom)

^℘In this study, spine density in somatosensory cortex was elevated at 1, 7 and 8 weeks of age, but not at 2 weeks.

^†This is the only study that has reported a decrease in spine density in neocortical neurons (dissociated, E16+20div).

^*This study actually reported a lower than normal spine density in Fmr1 KO mice.

^¥This study found that spines were not immature in CA3; also, they found no change in average spine length.

^‡This study found that spine length was normal in neocortical neurons (dissociated, E16+20div).