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First published online September 22, 2005
doi: 10.1242/10.1242/jcs.02581

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Chromosome architecture in the decondensing human sperm nucleus

¹ The Jones Institute for Reproductive Medicine, Eastern Virginia Medical School, Norfolk, VA 23507, USA
² Institute of Cytology, Russian Academy of Sciences, St Petersburg, 194064, Russia

View larger version (62K): [in a new window]   Fig. 1. Compact CTs in human sperm nuclei. (A-C) Localization of chromosome arms using FISH with arm-specific microdissected DNA probes. Left panels, DIG-labeled q-arm probes detected with anti-DIG-FITC; middle panels, BIO-labeled p-arm probes detected with avidin-TR; right panels, images of the same cells registered using triple-band-pass filter, total DNA counterstained with DAPI. Position of the tail attachment (basal part of nuclei) is indicated by a star. (D) Non-random intranuclear localization of the compact CT of sperm chromosomes. Cumulative scheme, showing positions of CTs registered by FISH. Sperm cell nuclei is approximated by an ellipse and is divided into four zones, starting from the basal side that is determined by tail attachment site.

View larger version (66K): [in a new window]   Fig. 2. Internal organization of CTs. (A) Identification of the TEL and CEN domains in CHR5 using simultaneous hybridization with arm-specific and subTEL-specific probes. Both rows of panels from left to right: DIG-labeled p-arm painting and q-arm subTEL probes (qTER) were detected with anti-DIG-FITC; BIO-labeled q-arm probe was detected with avidin-TR; merged image and image registered with triple- band-pass filter, total DNA counterstained with DAPI. (B-D) Localization of chromosome-arm domains with two-color FISH (p-arms, green; q-arms, red). Representative sperm cells are shown in the three rows of panels (from left to right): images taken with a selective green-filter; images taken with a selective red-filter; merged red and green images; images acquired using triple-band-pass filter. To the right of images: matching schemes of the chromosome-arm paths indicating the localization of TEL (T) and CEN (C). Position of the tail attachment (basal part of nuclei) is indicated by a star.

View larger version (37K): [in a new window]   Fig. 3. Unfolding of the q-arm of chromosome 1. (A) Representative images of the CHR1 q-arm in sperm cells taken with triple-band-pass filter (DNA counterstained with DAPI, blue) or selective FITC-filter (green). (B) Selection of typical images of the CHR1 q-arm domain arranged in the order of nuclei size. L-length of the long nuclear axis. Position of the tail attachment (basal part of nuclei) is indicated by a star. Arrowheads in A and B show condensed heterochromatic regions and white lines the CEN domain. (C) Correlation between the lengths of CHR1 q-arm and the long nuclear axis in sperm cells. (D) The width of the CHR1 q-arm chromatin fibril does not depend on length of the long nuclear axis. D and C, solid bold lines show best-fit regression, dotted lines-confidence intervals. (E) Frequency distribution of the CHR1 q-arm widths registered over the wide interval of sperm nuclear sizes (0.4 µm>L<2.6 µm).

View larger version (51K): [in a new window]   Fig. 4. Internal organization of chromosome arm fiber. (A) Representative images of CHR1 in cells with decondensed CTs. Representative sperm cells are shown in the four rows of panels. CHR1 q-arm, green; CHR1 q-arm, red. (First row) First and third images were taken with triple-band-pass filter; second and fourth with green-filter. (Third to fourth row, columns from left to right) Images taken with triple-band-pass filter; selective green-filter; selective red-filter; merged red and green images. (B) Enlarged images of the boxed areas. Globular chromatin nodules of approximately 500 nm are indicated by arrows. Arrowheads point at the double rows of globules that form fibers of chromosome arm chromatin.

View larger version (21K): [in a new window]   Fig. 5. Chromosome architecture in human sperm cells. (A) Model of sperm nuclear architecture proposed on the basis of CEN- and TEL-domain localization (Zalensky, 1988; Zalenskaya and Zalensky, 2000). Only two CTs (orange and pink areas) are shown. They stretch between the sperm chromocenter formed by an association of CENs (red circles) and TELs (green circles), which form dimers at the nuclear periphery. (B) Levels of chromosome architecture in human sperm nuclei, arm-specific chromatins are shown in red and green. (a) Compact CT, p- and q-arms are tightly merged. (b) Extended chromosome hairpin, arms are intertwined or stacked in antiparallel; (c) 1000 nm fiber of an individual arm. (d) Two rows of 500 nm nodular structures that form 1000 nm fiber. (e) Chromatin nodules hypothetically consist of nucleoprotamine toroids. CEN, centromere; T, telomere. (C) Donut-loop model (Ward and Ward, 2004). A thinner chromatin thread, presumably nucleohistone, attached to a nuclear matrix (NM) connects nucleoprotamine toroids. Each toroid consists of a packed 50 kb DNA loop.

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