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The process by which excitatory neurons are generated and mature during the development of the cerebral cortex occurs in a stereotyped manner; coordinated neuronal birth, migration, and differentiation during embryonic and early postnatal life are prerequisites for selective synaptic connections that mediate meaningful neurotransmission in maturity. Normal cortical function depends upon the proper elaboration of neurons, including the initial extension of cellular processes that lead to the formation of axons and dendrites and the subsequent maturation of synapses. Here, we examine the role of cell-based signaling via the receptor tyrosine kinase EphA7 in guiding the extension and maturation of cortical dendrites. EphA7, localized to dendritic shafts and spines of pyramidal cells, is uniquely expressed during cortical neuronal development. On patterned substrates, EphA7 signaling restricts dendritic extent, with Src and Tsc1 serving as downstream mediators. Perturbation of EphA7 signaling in vitro and in vivo alters dendritic elaboration: Dendrites are longer and more complex when EphA7 is absent and are shorter and simpler when EphA7 is ectopically expressed. Later in neuronal maturation, EphA7 influences protrusions from dendritic shafts and the assembling of synaptic components. Indeed, synaptic function relies on EphA7; the electrophysiological maturation of pyramidal neurons is delayed in cultures lacking EphA7, indicating that EphA7 enhances synaptic function. These results provide evidence of roles for Eph signaling, first in limiting the elaboration of cortical neuronal dendrites and then in coordinating the maturation and function of synapses.dendritic spine | neurogenesis | synaptogenesis

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Purpose This article examines if longer posterior spinal fusions with instrumentation (PSFI) into the lumbar spine (L3/4) alter spinopelvic parameters compared with selective fusions to T12/L1/L2 in adolescent idiopathic scoliosis (AIS) patients. Methods We analysed radiographs of 84 AIS patients, 58 (69%) females and 26 (31%) males, who underwent PSFI at an mean age of 15 years ± 2.5 years, range 10 years to 21 years, between 1st January 2007 and 31st December 2014. Radiographic parameters were measured pre- and post-operatively at most recent follow-up (range 2 years to 8.2 years): pelvic incidence (PI), lumbar lordosis (LL, L1–S1 and L4–S1), sagittal vertical alignment (SVA), scoliosis angle and proximal junctional kyphosis (PJK). PI–LL was calculated. Data was analysed using t-tests or Wilcoxon rank-sum tests. Results In total, 32 patients underwent a selective fusion with lowest instrumented vertebra (LIV) T12–L2, and 52 patients underwent a fusion with LIV L3–L4. In both groups, scoliosis angle was significantly corrected at follow-up (p < 0.005). Pre-operatively, both groups had similar LL (L1–S1) and PI–LL. Post-operatively, LL increased in the L3–4 fusion group (p < 0.005) but did not change in the selective fusion group (p = 0.116). This change in LL in the L3–4 fusion group affected the post-operative PI–LL (T12–L2 fusion -4.9° versus L3–4 fusion -13.6°, p = 0.002). No differences were seen in PI, SVA or LL L4–S1 between groups. Radiographic PJK occurred in seven of the L3–4 patients with and without PJK (noPJK –8.8° versus PJK –25.8°, p = 0.026). Conclusions In patients who underwent a fusion ending at L3 or L4, LL was increased. This altered the PI–LL relationship, and appeared to increase the risk of PJK. Level of evidence III