Math5 expression and function in the central auditory system

• Published in: Molecular and cellular neuroscience Vol. 37; no. 1; pp. 153 - 169
• Main Authors: Saul, Sara M., Brzezinski, Joseph A., Altschuler, Richard A., Shore, Susan E., Rudolph, Dellaney D., Kabara, Lisa L., Halsey, Karin E., Hufnagel, Robert B., Zhou, Jianxun, Dolan, David F., Glaser, Tom
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.01.2008
• Subjects: ABR latency; Animals; atonal; Auditory Pathways - cytology; Auditory Pathways - metabolism; Auditory processing; AVCN; Basic Helix-Loop-Helix Transcription Factors - genetics; Basic Helix-Loop-Helix Transcription Factors - physiology; beta-Galactosidase - metabolism; bHLH; Binaural integration; Bromodeoxyuridine - metabolism; Calyx of Held; Cochlear nucleus; Cochlear Nucleus - anatomy & histology; Cochlear root neurons; Cre recombinase; Evoked Potentials, Auditory, Brain Stem - genetics; Fluoro-Gold; Globular bushy cells; Inferior colliculus; Interaural intensity difference; Interaural time difference; Kcnq4; Kv1.1; Kv3.1; MafB; Math1; Math5; Mice; Mice, Inbred BALB C; Mice, Transgenic; Mouse; Multipolar cells; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - physiology; Neurons - metabolism; Phase locking; PVCN; Rhombic lip; RNA, Messenger - metabolism; Spherical bushy cells; Stilbamidines - metabolism; Tract-tracing; Globular bushy cells; Inferior colliculus; Tract-tracing; Phase locking; Cochlear root neurons; Rhombic lip; bHLH; PVCN; Kcnq4; Kv3.1; Interaural time difference; Kv1.1; atonal; Math1; ABR latency; Calyx of Held; Math5; Cochlear nucleus; Fluoro-Gold; Binaural integration; Cre recombinase; Mouse; MafB; Spherical bushy cells; Multipolar cells; Interaural intensity difference; Auditory processing; AVCN
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2007.09.006

The basic helix–loop–helix (bHLH) transcription factor Math5 ( Atoh7) is required for retinal ganglion cell (RGC) and optic nerve development. Using Math5-lacZ knockout mice, we have identified an additional expression domain for Math5 outside the eye, in functionally connected structures of the central auditory system. In the adult hindbrain, the cytoplasmic Math5-lacZ reporter is expressed within the ventral cochlear nucleus (VCN), in a subpopulation of neurons that project to medial nucleus of the trapezoid body (MNTB), lateral superior olive (LSO), and lateral lemniscus (LL). These cells were identified as globular and small spherical bushy cells based on their morphology, abundance, distribution within the cochlear nucleus (CN), co-expression of Kv1.1, Kv3.1b and Kcnq4 potassium channels, and projection patterns within the auditory brainstem. Math5- lacZ is also expressed by cochlear root neurons in the auditory nerve. During embryonic development, Math5-lacZ was detected in precursor cells emerging from the caudal rhombic lip from embryonic day (E)12 onwards, consistent with the time course of CN neurogenesis. These cells co-express MafB and are post-mitotic. Math5 expression in the CN was verified by mRNA in situ hybridization, and the identity of positive neurons was confirmed morphologically using a Math5-Cre BAC transgene with an alkaline phosphatase reporter. The hindbrains of Math5 mutants appear grossly normal, with the exception of the CN. Although overall CN dimensions are unchanged, the lacZ-positive cells are significantly smaller in Math5 −/− mice compared to Math5 +/− mice, suggesting these neurons may function abnormally. The auditory brainstem response (ABR) of Math5 mutants was evaluated in a BALB/cJ congenic background. ABR thresholds of Math5 −/− mice were similar to those of wild-type and heterozygous mice, but the interpeak latencies for Peaks II–IV were significantly altered. These temporal changes are consistent with a higher-level auditory processing disorder involving the CN, potentially affecting the integration of binaural sensory information.