Evolutionary significance of delayed neurogenesis in the core versus shell auditory areas of Mus musculus

Abstract

Early comparative embryogenesis can reflect the organization and evolutionary origins of brain areas. Neurogenesis in the auditory areas of sauropsids displays a clear core-to-shell distinction, but it remains unclear in mammals. To address this issue, [3H]-thymidine was injected into pregnant mice on consecutive embryonic (E) days (E10-E19) to date neuronal birthdays. Immunohistochemistry for substance P, calbindin, and parvalbumin was conducted to distinguish the core and shell auditory regions. The results showed that: 1) cell generation began at E13 in the external or dorsal nucleus of the inferior colliculus (IC), but it did not start in the caudomedial portion of the central nucleus of IC, and significantly fewer cells were produced in the medial and rostromedial portions of the central nucleus of IC; 2) cells were generated at E11 in the dorsal and medial divisions of the medial geniculate complex (MGd and MGm, respectively), whereas cell generation was absent in the medial and rostromedial portions of the ventral medial geniculate complex (MGv), and fewer cells were produced in the caudomedial portion of MGv; 3) in the telencephalic auditory cortex, cells were produced at E11 or E12 in layer I and the subplate, which receive projections from the MGd and MGm. However, cell generation occurred at E13-E18 in layers II-VI, including the area receiving projections from the MGv. The core-to-shell distinction of neurogenesis is thus present in the mesencephalic to telencephalic auditory areas in the mouse. This distinction of neurogenesis is discussed from an evolutionary perspective.

Erbin and ErbB2 play roles in the sexual differentiation of the song system nucleus HVC in bengalese finches (Lonchura Striata var. domestica)

“…Those incubated with biotin-conjugated biotinylated secondary antibody were then reacted with ABC (Vector Labs; 1:200 in 0.5% Tri-tonX-100/PBS) and visualized using the DAB reaction. The specificity of antibodies in the brain of songbird has been verified in previous reports, including anti-HuC/HuD (Louissaint et al, 2002), anti-NeuN (Scott and Lois, 2007;Zeng et al, 2009), and anti-cGABA (Pinaud and Mello, 2007). The antibody specificity was also confirmed from our staining patterns which were similar to related reports (Pinaud and Mello, 2007;Chen et al, 2014).…”

Histone methyltransferase Suv39h1 deficiency prevents Myc‐induced chromosomal instability in murine myeloid leukemias

“…This is in agreement with the observation that knock-down of Rad50c and Smc5 inhibits ALT-induced telomere maintenance, resulting in critically short telomeres (Potts and Yu, 2007;Zhong et al, 2007). Downregulation of Fen1, FancA, and Mus81 prevents telomeric recombination required for ALT (Fan et al, 2009;Zeng et al, 2009). Thus, a more effective elongation or stabilization of telomeres in Myc-driven myeloid leukemias by ALT mechanism may have Suv39h1-wt and 7 Myc/Suv39h1-minus mice were analyzed.…”

Distinction in the immunoreactivities of two calcium‐binding proteins and neuronal birthdates in the first and higher‐order somatosensory thalamic nuclei of mice: Evolutionary implications

“…Compared to the distribution of CB cells in primates, the present study indicated that many fewer CB cells appeared in the "matrix" of the VPM and VPL in mice. It needs to be mentioned that nearly no CB cells are found in the core auditory nuclei in the mesencephalon or diencephalon of chick (Zeng et al, ), but some are located in the mouse (Zeng et al, ). Based on the above analysis of the actions of the higher‐order modulatory cells (including CB cells in the matrix of the VPM and VPL), the lack or the large reduction in the number of CB cells in the primary (or the first‐order) thalamic relay nuclei might suggest a weak modulation to the transferring thalamocortical information or to the corticocortical communication in mice and birds in comparison with that in primate species.…”

“…Additionally, the generation of cells in the core auditory regions of amniotes is significantly delayed in the ventricle zone relative to the cells in the diffuse regions (Zeng et al, , ,b, ), and positive CB staining occurs earlier than PV immunoreactivity during embryonic development (Xi et al, ). In light of the concept of Von Baerian recapitulation, early animal embryos within a taxon resemble each other, and the degree of resemblance decreases as development proceeds (Gould, ; Butler, ; Northcutt, ).…”